I read a few things on what it may be but basically I want to describe my problem and see if anyone can help me troubleshoot. I have a 94 cx w/b18b1 swap. I know I need an o2 but I don't think that would really affect my idle. Most of the time when I start my car from a cold start my idle goes up and down until it warms up. It sounds like I have a supercharger, like a whinning noise. But my idle eventually always comes down to normal. Say its all warmed up and idling fine, if I'm on the gas or just give it gas and let go, the idle won't just come back down/drop down. It'll stay up for sec and gradually come back down to normal. Anyone have any ideas. It sounds like I have a supercharger. Would that indicate like a vacuum loss? Thx for any troubleshooting ideas.