have on my 1998 502efi with thru hull exhaust the corsa tips with built in mufflers that are always on . they do help alittle to quiet down the boat but are they robbing me of any performance ?

The 6" diameter are good for 525 Hp the 6 1/2" are good for 650 Hp

I replaced two pair of 6" Corsa mufflers on a Formula with 525efi's and gained 2-3 mph gps and 150 rpm. Probably cost 30 hp on each motor!