noticed it after i changed my t-stat. coming from the back passenger side. it goes away with a lil trottle, but returns when at idle. what could it be. i did a search and a similar thing happend with a 94....he had a problem with his IAC tube....he was told that 94-95's had a prob. with that tube...and there was an updated one avail. i assume that my 96 4.6 has the updated tube. What could it be!!!