What's a good spark plug to use for a 96 LT1 with a Vortech supercharger (6-7 PSI boost) and 42 pound Motorsport injectors? Other than headers and better exhaust the rest of the car is stock. I just put in NGK TR55IX's (part 7164), gapped them at .044 and the car runs great cold but when it warms up and I get on it the car spark-knocks like crazy and occasionally backfires. The NGK's out of the box and the stock Delco plugs I took out were at around .060 gap. The car ran great with the Delcos, I just changed them over to the NGK's per the tuners advice. (I got a mail order tune on it for the 42 pound Ford injectors and to raise the rev limiter to 6500). Any help would be apprecitated! I see plug gaps ranging from .032 all the way up to .060 on these cars.