You do not wanna run it lean for very long esp at high revs rich is giving it a little more gas so it kinda cools down the motor but if its to rich it will run like dog shit and lag out in the band or at wot so a plug chop is a must
He isnt running a snokle on there and im sure he has a k&n so like i said id go 280 plug chop and adjust according. I have fmf fatties with same silencers im 64.5mm with boysen reeds with 290 main and 27.5 pilots but 1200asl