i got a 96 RS 420A with a completely rebuilt engine. my problem is that since i put everything back together it wont idle smooth. i have to keep tightening the throttle cord to keep it running. what it does is when u start it up it idles like it in retard timing mode. i've checked my timing marks and everything looks good. the car set over the winter with a full tank of gas so im kinda thinking maybe my fuel filter/pump might be going bad or vacuum leak somewhere...ive tried almost everything and running out of ideas...so any help would be greatly appreciated. thanks

Do what was mentioned above also if you didn't use any Stabil or any kind of treatment for the gas, it could be bad if its sat for a very long time. I would start with the IAC.