What kind of plug came with the engine? Not that that's a good indication...I've had some cold Rossi plugs included in the 'package' that weren't even close to what was needed. Believe it or not, I've had great results (or is it luck?) with el-cheapo Thunderbolt Performance #3 plugs in high-nitro, high-rpm applications (on and off-road 1/8 scale cars) freakin' high-buck engines. They consistently bested OS #8s, #3s, and MC-59s in performance and reliability. Diamonds in the rough for sure...but I guess it depends on who you ask...and who there sponsors are
-Tom