I think everyone is missing the point of why spend money trying to diagnose when diagnosing the right problem will save you money.

A while back, I thought I had a sticky tstat. I didn't go out and spend the $13 replacing it, I tested it in boiling water and it opened and closed normally.

Turned out I had a pin hole in a water line coming off the throttle body. And I had spare hose, so that fix was free.

Just another "case in point"...(I like that term, I may steal that )