Has anybody had any luck with HP upgrades on 500s efi ? I have a 02 vyper and thinking of doing something .

It really depends on what kind of power you want to make, if its in the budget, Whipple it, the internals will handle it, as long as you dont go crazy on boost, there's one in the classified's for 6K

I second the whipple idea,,best bang for the buck.

Depending on how far you want to go do forget about drive upgrades

Do the throttle body and ignition upgrade do much?

The million dollar question, do you have to crack into the engine at this time?

not really, that plenum wont flow much more air, heads and cam is where the power is made, if your not going to put a huffer on it.

Hard to gain much power keeping her N/A without dumping as Much money as adding a whipple or procharger. I had 230 trouble free hours with my properly setup procharger......but had drive issues.

Don't forget about your drives! The only upgrade worth throwing money at is a Imco SCX. Now your into your boat for double what its worth.

Might as well sell her and buy something that's already faster.....

The motors have 350 hrs ,the heads were gone through at 300.the boat has xr drives . I'm thinking of opening up the motors at 400 hrs. It currently runs mid to low 80s.

Your running low to mid 80's with stock 500 efi's ??