Whether or not they need to "prove" anything it'll be a huge headache for you. Might as well avoid the whole situation by going in stock if you have to.
I would never do work at the stealership unless its warranty covered work. They're are plenty of better qualified Indy shops out there.
DP's are fun as hell, but a bitch to install/remove if you're not set-up properly at home. The exhaust gasket is also only reusable a few times - it's not invincible so eventually of you've done enough swaps I'd replace it. Otherwise, enjoy the car dude!
And stop going to the stealership lol!