I have similar problems, dive bombing rpms when putting it in neutral and it sumbles when accelerating at anything but WOT. I've checked my IACV stuff and all seems to be be ok. I don't appear to have an intake leak. So I'm going to keep doing all the tests I can find in my FSM for the symptoms I'm experiencing. Some quick and easy things to do without giving much thought is to check timing, check tps voltage, check your MAF ground. Here's a link to a thread which lists stuff you can check.
http://www.sr20deforum.com/showthrea...threadid=38146
