Great info, thanks. I have a line on a #25 with both DISA valves for $350, so I may go this route if the heat sink isn't that expensive. I don't mind running without the cosmetic engine cover. I come from the motorcycle world, so I've never heard of a heat sink before. Any idea on the price or part number?
Any idea where the hp disparity between the #25 engines and the #23 ones lies? I'd hate to do the entire swap only to end up with just +10hp.