Today I took out the 20mm end cap and tried the unused pea-shooter cap. The rackit end cap has a really good coating of perfectly back carbon(?) deposit on it. I recall a loaner 520EXC that I was allowed to use during an intenst week in San Rafael Swell. We covered all, from sand dune WFO riding to 2h in 1st and 2nd in 5MOH. The inside of said 520 muffle cap was a clean as possible, sliding your finger through it would make you dirty at all. Hence: Are the EFI WR450Fs running super rich in racing kit mode, w/o closed loop lambda sensor? I've got me the idle CO adjustment tool, but what about the rest of the power band? Is anyone out here adjusting fuel amount with the Power Tuner guided by amount of carbon in the end cap? Personally, I loved that 520EXC's tuning work, especially because she was combusting so clean.