Donzi22zx

I have a 99 Donzi 22zx with a 454 mag EFI with a bravo 1 drive/ 1:50r with a 23p mirage plus prop. What performance mods does everyone recomend, I currently have a rex marine K&N air filter and have removed the corsa quick & quiet exhaust, and added MSD plug wires with NGK v power spark plugs. I think I need to replace my exhaust headers because one is running very hot(right side)and very rusty. I am thinking of buying Stainless Marine headers and risers? and maybe a MSD ignition box and possibly roller rockers. Anyone with experience on these motors or on my boat please help. So far the boat has run 71.3mph on GPS/ garmin 5 .
Thanks Bill