Originally Posted by Prerun4fun13

I am gonna agree with detonation because it only happens under load. Try having a scanner hooked up and drive it around and see if you have any. What grade gas are you using?? I am gonna disagree on a collapsed lifter because if it was collapsed i am sure it would make noise all through out the RPM not to mention it only happens when he drives the car... This is a head scratcher, did the techs at the shops you took the car to road test the car???