That's a question for your insurance company. I used State Farm for years and they never questioned the legitimacy of my aftermarket parts if I produced a receipt. Performance parts or otherwise, it never mattered.
Now I'm with Allstate and they require a rider after a certain dollar amount to account for those added parts and it bumps the premium. I don't know what the threshold was, but I went over it pretty much with just the procharger's cost.
I have everything with Allstate - home, boat, multiple cars, motorcycles, and this rider thing wasn't something I expected. I still get a killer deal overall and I've known my agent so long I simply don't want to cut to someone else over something so minor..
I'd be up front and ask the agent direct, you don't want to find out after the fact that they specifically don't cover...