Last nite I had my buddy, who works for a Chevy Dealership, program a new key for me so I can use a remote starter, he owns his own Tech II. Anyway, I offered to let him take it for a spin. When I told him to punch it,(motor wasn't cold), he and I both heard what we feel is detonation,(popping thru the exhaust under acceleration). Has anyone else had this problem?. I am using premium gas (Mobil or Shell).