losing sleep

I have a 99 Avenger in my shop that idles rough but runs good. Car stalls at every intersection. Corrected problem somewhat with new IAC valve. Vehicle also runs for about 10 to 15mins then CEL comes on and wont go over 4000 rpms. Cant remember code number but it is MAP pneumatic change. This car was at Chrysler and owner was told it had bad fuel. I dont think so. It has also had lots of parts thrown at it, including MAP, TPS, ECM, plugs, wires, intake gasket and God knows what else. If you've seen this b4, please advise. I'm pulling what little hair I have out!!! Engine is 2.5 V6 Mitsubishi.