I've read a lot of posts about high rpms and idles but none that are quite like mine. I have a 97 2.0 manual transmission. When the IAC is plugged in the RPMs are way up when in neutral coast or at idle but when I unplug the IAC the RPMs are fine and the idle is fine. I have replaced vacuum lines, cleaned both the TB and the MAF , bench tested the IAC with 12 VDC source (works fine) and used starting fluid to find any vacuum leak. No luck. I'm pretty sure I have a vacuum leak. I'll grab a mity Vac and doing some more investigating. Any other ideas or thoughts are much appreciated in advance.