rough idle

I have a 91 n/a supra w/ a very rough idle it idles well a first start up but then sputters out. Runs great on road this is a suck ass proble when you go to stop. Any one got any suggestions, HELP!!!

What about your oil pressure. Does it stay fairly decent or does it drop suddenly at idle or anything like that?

I have had a couple cars that had a similar problem. In both cases it was the catalytic converter. Just a suggestion from a few bad experiences of my own.

I figure the c.c might be messing with it consider it has 2 bolt on ones. I figured someone couldn't pass emisions and put on as many as they could. And the oil pressure stays fine.