Let me start off by saying the car idles perfectly fine. It only happens when you rev it or shift into neutral. It seems like any time after like 2k RPM it will drop down to 500, stumble for a second and go back up. So if i shift out of second into neutral at 3k RPM's it will drop to 500 and back to 980. I just had the PCM programmed by Ion and it runs great. I checked all my vaccume connections and their fine. Im kinda clueless on what it can be.

 

Could that be some kinda backpressure issue?
Bill

 

Funny you said that. Im running it pretty much with an open Y-Pipe right now. Is it possible that no backpressure will do that?