Vibration, Vibration at certain RPM's Options

[rapid36]

Hey guys I have a 94 celica st automatic transmission, I brought this car back to life after 3 years of sitting, The car ran fine and everything but when i was doing exhaust work i put everything back together and now all of a sudden I have a vibration at 900 and below rpm and anything over 3500 rpm it makes the vibration. I ruled out the exhaust since I just got done redoing the entire system, for good measure though i will be double checking this. It sounds like its coming from the back of the motor and on the driver side, I suspected a transmission problem? So I flushed the whole system and put in brand new fluid and filter as well. I can drive the car around just fine and never over heats and the vibration only comes at certain rpm NOT SPEED. So I thought what the heck why not take out the starter and see whats going on with that. So I took out the starter and it looks fine, no chipping of gears or anything. The engine is very stable and has no idling problems so i ruled out being an engine performance problem, I also replaced all of the engine mounts and still no luck. Anyone have an idea of what this could be?????