I do not want you to waste time/money and become frustrated so here is my story...
My Son did absolutely everything to his 3.0L and the car ran slower, he went from 16.10 in the 1320' to running 16.80 in the 1320',
He like me was a Bracket Racer,his original goal was to get into the 15's so he could run two classes at Atco Raceway (Pro 15.99 cut and Street 12.00 and up)
After witnessing him spend hours and hours and tons of $$$ over a three year period for nothing but aggravation and frustration I am not a fan of "Attempting To Mod/Tune a 3.0L".
The mods were not done all at once, the exhaust was on there when he was running 16.10 and as he added mods such as the ported plenums he got slower, the more he did the slower he got.
He had the plenum and intake ported, added spacers, had the heads ported with a 3 angle valve cut and had the manifolds/spacers/gaskets port matched to the head, installed a 3.8L Mini Van TB, Cold Air Intake (real cold air, plumbed to the opening where removed fog lamps were), 3" Exhaust with Low Restriction Cat and Muffler (got ticketed twice for excessive noise) and work done on the A604 (shift kit, heavy duty clutches, final drive gears from a mini van, torque converter), installed a manual fan switch to keep the engine at a lower temp when racing (he experimented with different temps), installed a trans temp gauge, auxiliary trans cooler, etc and a Wideband O2 Sensor (the car was running about 11.5/1 @ WOT (You cannot install an Adjustable FPR without modifications to the Fuel Rail), Street Slicks and Air Bags in the rear to prevent squatting on launch which unloads the front wheels.
It made absolutely no difference if he shifted or let it shift on its own.
On a couple of occasions I verified the basics for him just to be sure they were correct...
Compression/Cylinder Leak Down, Fuel Pressure, Injector Flow, Map Sensor Response and Ignition Timing at all RPM/Load Conditions, wish my 2.2L was as sound as his 3.0L.
So, thats my 3.0L experience/story, take it for what it is worth.
Others will tell you that the 3.0L mods work to improve performance but you cannot prove it by me.
FYI..
Giving suggestions on what may or may not have been wrong with his setup is now a MOOT POINT since he sold the car a year ago with all types of additional parts for $500.00