i'm pretty sure engine has stock guts. all i've done is added 4 degree timing key,sst fmf headers,powercore 2 muffs, 35mm pwk's, stock reed cages with vito's carbon flex stage 2 reeds, prodesign cool head with 19cc domes which i were told were for a stock engine. and i don't know what plug chopping is.that's pretty much it. I live about 300 ft above sea level and jetted for that. I even ran it once came back, checked the plug and it was a good tan color. so i'm not sure what to do.