I am going to tell you as much as I know about the car to help pinpoint the causes" I am having. I apologize for this being so long. Well for starters I just bought this car, and on the test drive everything seemed ok until I got it home. I drove this car about 165 miles back to my place non stop on the highway on a cool day, and when I finally had to stop at a light getting off the freeway as I was slowing down I noticed that around 50 MPH the tach would jump up and down when downshifting, not Spastically but enough to notice. It always does this at about 45 to 50 even if I just let off the gas and coast it will bob up and down. the other problem is when I just about come to a full stop you can here the tranny downshifting and at the last second the car comes to an abrupt stop followed buy this kind of surging like sound and then the car will move forward. It gets worse the more I drive, I usually think it will die but it doesn't. It idles really high on startup and when stopped and seems to idle higher the more you drive. I even noticed when I let off the accelerator it will move forward like you just pressed on the gas to accelerate, it will even shift through the first gear without your foot even being near the gas pedal if I let this continue it will just gradually go faster. On top of all that the car seems to almost overheat. I checked the radiator for oil and saw none as well as the overflow tank and none there; radiator was replaced sometime before I acquired this vehicle. When driving the temp gauge is usually just below half, if I stand still in traffic gauge rises and keeps going, but when moving it will slowly drop back down. I was looking for a EGR valve and went to a Dodge dealership to get the part and when I pulled into there service garage and got out I turned around to see antifreeze was gushing out of the overflow tank and BOILING!!!! OH GREAT!!!!! Luckily it still drives, this happened to me twice the second time it wasn't so bad. All the work that has been done to this car since I acquired it has been new front and rear valve cover gaskets, they were leaking pretty bad, new EGR valve, before it was running poorly and idle was low and spastic as well as the high idle which IT STILL DOES!!!! New plugs and wires all hooked up correctly. Could it be degraded tranny fluid and or computer update? A new thermostat? Sensor or fan relay? VACCUME LEAK!!!!!!! I am seriously at a total loss with this; any help would be much appreciated. If you need to know this is an automatic, I really like this car and don't want to give up on it. Thanks to all who respond!