if its not the ect (engine coolant temp) sensor then try the act sensor (brown one on the plenum)
could also be buggerd map sensor or a split vacuum pipe off the plenum

easy way to test if its the ect or act sensors is to start the engine and let it idle, pull the plug of the sensor, then breifly bridge the 2 contacts on the plug with something metal.
doing this will make the ecu think your engine is warm and cut the fuel back
if doing this makes the car run better then you know uve just found the bad sensor!
WARNING doing this can sometimes blow the 30amp fuse found near the ecu. no big problem but just lettin you know incase it happens and you wonder why your car wont start anymore