Go speak to your service department. I was completely up front with them about my outlandish stack of mods, and their position was that if I was sure a problem stemmed from one of my mods, I should not bring it in, but if I was sure it was not, they would gladly cover the repair under warranty. Assuming that same policy is in place at your local service dept (how they handle these things can vary) then the only warranty voiding you'll be doing is on the handful of things that could go wrong from telling the engine to run properly. Which would be... hmm I can't think of anything. But lets stretch and say spark plugs, injectors, rings... would that be too high a price to pay, to not have those warrantied? At any rate you could still expect your drive train, your brakes, your radiator, so on and so forth, 99% of the car still to be covered since there's no conceivable way the tune could have affected them.
That's with the total honesty policy. If you use Trifecta tune, it comes with a transparency mode which has proven invisible to dealers (even to one who knew it was there and was deliberately looking for it), so if you use the "don't ask, don't tell" approach, you almost certainly won't have to worry even about those few items. And since it is nearly inconceivable that a tune would damage any of them, why should you?
I'm running 230+ hp thru this engine, for the past 5000 miles or so, and it hasn't had any complaints, I'm pretty sure just going to 150 or so isn't going to to bung it up much.