Marks Express

Hi everyone, I’m hoping someone can shed a little light on my problem.

I have a 2006 Express with 118,000 miles on it. Never had any issues. 2 weeks ago my starter died and I replaced it. After installation I reconnect my battery and upon starting it the idle was very weak. Over a few days it went back to normal. However, ever since then after about 20-30mins of driving when I come to a stop the idle drops and idles really rough. Then when I try to take off there is very little power. Sometimes the check engine light flashes, sometimes it doesn’t come on at all.

I hate to be one of those “replace parts guys” but from my mechanics recommendations so far I’ve:

-Replaced the IAC valve
-Cleaned the butter fly in the throttle body
-Replaced all plugs, wires, coils
-Replaced a clogged cat

My mechanic scanned the van (of course idling smoothly in his presence) and all it read was “misfire.”

Been chasing this ghost for 2 weeks. Any help and I will praise your name to everyone for the rest of my life!