95 Chevy Lumina APV stalling problem

I have a 95 Chevy Lumina 7 passenger van that is stalling. We start the engine and it idles fine for a second then starts to sputter until it finally dies. Sometimes it will pick back up but then sputter back down and die. If it doesn't die right away, as soon as we put it in drive or reverse it starts sputtering and dies. All the vacuum hoses have been checked and replaced. It has a new MAF sensor and TPS sensor now. Still didn't help the problem. We tried to have it scanned for codes but it showed no codes. It has a new fuel pump as well. We also put in a new fuel filter and air filter. We did take off the IAC sensor and checked and measured it. It was pretty black so we cleaned it and also removed the throttle body and cleaned it up. Any ideas would be much appreciated. Thanks.