has any sonic owners with twin 496 ho application tried upgrading there engines with cmi's or other exhaust systems and what were the results in mph ?

I am not a Sonic owner but I do pilot a Fountain. Man-o-man
have you herd of the 525 probloms with suspect CMI header issues? BOO-COO exhasut flow reversion probloms is tanking the engines. Have mulitple boats in my area spending this season in the shop with major probs> from Formula, Fountain, Sunsation to Black Thunder. The 496s are proving to be the Iron Duke for Mercruiser. Dont touch them, they are as trouble free as your going to get.

If you have the aluminum manifolds I wouldn't replace them. Not much gains to be had vs cost. Remove the turbolators will give most of the benefits (10-15hp) of aftermarket manifolds and costs nothing. Some mild porting can get you the rest.

Yeah, but those CMI's make the boat sound great......would be real good paired with some select raylar pieces. Alum heads, intake, and cmi's...sweet.