[Tommy]

Kenny,
When I had my engine rebuilt with higher performance in mind, the builder installed a set of cool plugs to assure there was no pre-ignition or detonation that could have caused real damage. These plugs lasted longer than yours (about a thousand miles) before fouling, but I got tired of messing with them. So I looked up the heat range data on them and got a set one step warmer. They have worked fine with no fouling. .... If I were you, I'd try plugs one step hotter and see if that helped.