SC is acting up

Hey guys- got a issue that i am not able to iron out. need some expertise from you guys that own SC's...not a shop that thinks they know what a SC is. When i first start the superbird for the day(outside temp doesnt matter) she will start right up but when it comes down to idle it studders and/or just cuts out. will start right back up and do the same-this continues till i start it and just go...drive with both feet(brake and gas) till it warms up completely....this isnt much fun....once warm you wouldnt even know there is an issue. ok now for what has been done so far...no computer codes are showing...ive cleaned the MAF,scrubbed the throttle body... replaced the coolant temp/IAC/and TPS sensors. the shop did a intake pressure test and there are no leaks. please let me know if any of ya have had this issue PLEASE......thank you-thank you-thank you in advance for any ideas.

1990 SC automatic

If there are no vacuum leaks....I would lean towards an IAC issue...

Engine coolant temp sensor can cause similar issues as well. Even with out setting a code. Sensor resistance is wrong. Thinks engine is warm, thus leaning the mixture out and not running correctly till the engine is warmed up.

Dave/frdlvr30- Thank you for the info. the voltage to the IAC is changing which mean the computer is ok. the IAC is from Ford. its the 3rd one i put in...the shop said it must be the after martket part(BWI/Borg Warner)so i went to Ford. have changed the coolant temp sensor...guess its possible its a bad one. i did alot of tests b4 sending the car to a shop i just ran out of ideas. how would i test the coolant temp sensor to rule it out(or in) as the problem?