I have a 1993 Chevy Cavalier 3.1, 5 speed and it has a weird problem with hesitation. The car starts up and runs a little rough for 5 seconds or so then smooths out its idle really nice for about 3 seconds, then the check engine light comes on and it runs kind of average. I just put the engine in with about 100k on it and put all new gaskets on it. It will run good but will hesitate under load at RPMs under 2500 if you don't put the pedal down very hard or keep it very steady and smooth with lower acceleration. It runs very fast if you run it hard but drivability is poor for driving normal. I checked for vaccum leaks and it seems good. No stored problem codes in the computer. Any ideas?