I agree with my brotheren suggestions above. There is a long list of things you could do and knowing when to say 'uncle' is an important part of actually getting the project finished and having a good daily driver. Luckily, almost everything you can do comes in the form of factory parts that will simply bolt on. Over the years, Chrysler knew they had a winner with the 2.2 and 2.5 engine and that is exactly what they did, they upgraded pieces for more power and they are all simple bolt ons for the most part.
Here are a few of my thoughts...
If you have a mitsubishi turbo, from a performance point of view, that is probably the first thing that needs to be replaced. Others may argue that it is fine, but in the long run, at higher boost applications it just runs out of steam or is over reving and will self destruct eventually. It is small to spool quickly for drive-ability but it lacks a good top end. The Garrett turbo came in two basic flavors, we call them TI and TII style. The turbo is the same, only the cold side 'compressor' housing changes. IIRC the oil supply line is the same for either but the coolant line is shaped differently for TI and TII. There are stainless steel braided line replacements available from either turbosunleashed or fwdperformance. Early cars came with a 2.25" swing valve and exhaust to match. Later cars, like 89 to be specific, came with a 2.5" swing valve and a larger wastegate actuator. The 2.5" swing valve and a 2.5" all the way back exhaust really wakes up these cars and is a very good performance upgrade that requires no further tuning. One thing to note however, the swing valve is held on by 5 bolts that have been heat cycled hundreds of times and typically they do NOT want to come out so you can just swap swingvalves. Typically it takes a torch to heat the housing red hot where the bolt is to remove those bolts. If you are looking for a TII style turbo, I have both good used and rebuilt units.
A popular upgrade on the cylinder head that is a drop in and forget it upgrade is mentioned above, the "PT Lifter" upgrade. The standard 2.2 valve lash adjusters (lifters) tend to cavitate with air when run at higher RPMs for very long, so the engine starts to miss and looses power till the air escapes. The later 2.4 engine uses a lifter that has a check valve in it that allows air to escape, so it doesn't cavitate. But the 2.4 lifter is shorter than the 2.2/2.5 lifter, so we install a shim to compensate and bring the adjuster up to the right height. This upgrade makes the engine perform better at higher RPMs and also produces a nicer idle, quieter as well. I also sell the PT Lifters and special shims, both take-outs as well as new Mopar Performance.
The beehive spring update is also becoming more popular, to be brief, the 'beehive' spring is a conical spring that reduces the frictional power loss from high spring tension when the valve is closed. Due to the shape of the spring design, the spring tension increases as the valve is opened, reduces as the valve closes which helps the cam to turn more easily, it also allows the engine to rev faster and higher. When combined with the PT Lifter update, it makes for a very sweet head that can rev much better than stock. Much better. I also sell the beehive spring updates and use the valves available from turbosunleashed.
VALVE STEM SEALS
If you do anything with the springs off the head, that is a good time to replace the valve stem seals. The original seals were made of a hard synthetic rubber we call 'viton'. They are easy to install, they work fine, but after years they get hard, they crack, and they pop off. This makes the engine smoke. There is a myth that you can use hemi seals in the 2.2/2.5 head. It is a myth, none of them will fit and there is at least one good FAQ here on that subject. There are several opinions on the 'better' seal to use however, the best seal to use has to be the correct inner and outer height, have the correct inner stem diameter, and a sealing ring that matches the top of the valve stem guide. There is nothing at all wrong with using the original viton seal, however a positive clad seal design that came in later years is better. Positive means that it has a spring loaded stem seal, so over time, as the seal wears the spring maintains the seals integrity, clad means it is encased in metal, so the seal stays on the stem. And as it turns out, there is a seal that fits our applications perfectly, I sell these as well.
88 TBI AND PERFORMANCE CAMS
Another popular drop in mod is to swap the cam over to an 88 TBI cam. The problem is that almost none of the cams Chrysler put in our cars have any markings that distinguish one from the other. So, just because you find an 88 TBI car in the junk yard, you can't be positive it's an 88tbi cam because somewhere in that cars life it could have had the head replaced. The reason we like the 88TBI cam is because it has a grind spec that is very very close to the original 'slider' style cam. Early cars used a slider style cam with a more agressive grind, later cars use roller cams with a smoother grind. The cams are interchangeable but the followers are not, you can't use slider cams with rollers and vice a versa. Also be aware that there are "OSJ" cams. These are cams that are larger diameter than other cams. They exist because of a production mistake at Chrysler on the cylinder heads. They had a ton of heads that were machined with larger than standard cam journals and instead of junking thousands of heads, they had cams made with a larger diameter. Just be aware they exist and of course OSJ cams can not be used in non-OSJ heads and vice a versa. I have new in the box 88TBI cams available also. You can get brand new roller followers from one of our vendors as well. While on the topic of cams, turbosunleashed and fwdperformance both offer a nice collection of performance cams. The lower stage cams can be used with no or minimal modifications, the higher stage cams would require more like larger exhaust, larger injectors, turbos, FMIC, AFPRs etc to get the most out of them.
If you swap to the Garrett TI turbo it is also a great idea to at the same time add an intercooler. Some P-body cars came with an intercooler so you can sometimes find a P-body setup used. The P-body version mounds a little differently than the Daytona and Lebaron and Spirit, but those versions can also be used with only slight mounting modifications. Also note that P-body intercooler outlet necks are bent to the side a bit whereas Daytona style comes straight out and there are some variations of the radiator to intercooler brackets. It's best to find a matched pair intercooler/radiator combo.
The intercooled radiator is smaller than the standard TI radiator so you will need a TII style fan. Your TI fan might not fit, might be too large. If that were the case good used TII fans are still available but can be hard to find, they are 30+ years old. I sell a remanufactured TII style fan that also works perfectly on the GLHS cars.
INTERCOOLER PIPING and TII STYLE AIRBOX
If you add an intercooler, you will also need to add all the needed intercooler piping and hoses. You can typically find all the pieces needed using a "parts wanted" post. TII style air cleaner housings are pretty easy to find. The other hoses are out there but you may find yourself buying one here, one there. Some of them can be sourced new or used and on eBay in generic intercooler hose kits.
fwdperformance offers a custom calibration for these cars. A custom calibration is the best way to go for off the shelf performance. Basically, the engine controller is re-programmed to allow more boost and have an upgraded timing and fuel map for more power. The custom calibrations assume that you basically have a stock configuration otherwise. You can also learn how to do your own calibrations but will require some tools to do that as well as an engine controller that has a socket in it to allow you to burn and swap in new programs. There are also individuals here that will burn you a custom calibration. All you have to do is make a post for custom calibration wanted and I think someone will chime in. With a custom calibration, there is no need for the traditional "Grainger Valve"
There is one brake upgrade that you might want to research: SLH1. (S
ell 1) In brief, the SLH1 brake upgrade involves taking the (now) hard to find 84-90 Caravan/Voyager front brake calipers and a master cylinder from a Shelby and just bolting them on to you car. The Caravan/Voyager caliper is unique and is a 60mm piston design, larger than all the others. So this improve front braking force and is a direct bolt on for all our turbo Dodge cars. This also gives you the single pin Kelsey Hayes brake caliper that is much much easier to service the brake pads. I often offer complete SLH1 upgrades as I come across the hard to find needed Caravan/Voyager brackets. I have 1 set available right now. Here is a like to that for sale post: https://www.turbododge.com/forums/f7...grade-set.html
IMPORTANT TO NOTE: THE VACUUM/BOOST HARNESS
One thing that I know all the sage turbo Dodge enthusiasts will want you to know is that boost will put a smile on your face, it will also put a frown on your face! Our cars use a network of vacuum and boost lines with solenoids to monitor and control boost. If one or more of these lines leak under boost, all bets are off and you can easily over boost or run lean or both and wind up sacrificing a piston to the Gods of more boost. So, it's really important to make sure your entire vacuum and boost harness is up to par. The hard vinyl lines after 30 years become brittle and they will snap easily if bent, be aware of that. They can not be replaced with PVC line, it will melt in no time at all, they are vinyl and commonly called emission hose/line. Many of us replace the vacuum/boost harness with thick walled turbo silicone hose and a vacuum block. You can find all sorts of comments and posts and approaches to this by using the site search feature which we all recommend that you get to know. This site has years and years and thousands of good quality posts on almost every topic regarding turbo Dodge.
Your car probably came with a transmission called the "A520". It's a good transmission for that car. It has a stronger brother that is a bolt in compatible unit called the "A555". In brief, the A555 has a stronger gear set made by Getrag. One option that you have for either is to get an LSD and have 'posi-traction'. Both wheels delivering power to the pavement. It's a good thing especially when you start turning up the boost, one wheel tracsion is an issue that needs to be dealt with. You've really only got two good options, the Quaife LSD or the NEW turbosunleashed LSD. The Quaife is a standard in our community, it is also quite expensive. The new LSD from Chris at turbosunleashed is the best 2nd choice and is available at a much more attractive price point.