I think my throttle air bypass valve is going bad. The RPM's are at 2000 in Neutral. It always sounds like I want to race everyone at the intersection which draws unwanted glares. How can I diagnos this problem?

check the IAC vavle

I would bet money that your throttle position sensor or cold air intake temperature sensore needs to be replaced. your throttle position sensor is placed near the throttle body and the cold air intake temperature sensor is near the thermastat housing. I would buy a repair manual from your auto parts store and inside that manual tells you how you can test every sensor and valve...its a good investment.

check and dbl check for vacum leaks..I have a 98 150 that drove me crazy and the computor also and relaced alot of things only to find 2 leaks and never needed any parts..