Check and see if the yellow IACV is plugged in on the back of the engine. Maybe check the IACV adjustment, don't know how it would have gotten off. Doesn't really sound like that's what it is though. If you have availability of another MAF or ECU you could check for those, or if you know someone close, you would have already thought of that though. Check codes. More than likely a MAF problem. I had an issue with my daul MAF and SELIN set up and it wasn't reading one of the MAFs. Ran pretty rich at idle but it wouldn't rev past 3k.
