Not officially. Many dealers sell aftermarket tunes which are superior to the factory tune anyway. Every dealer I talked to said THEIR tune (which is likely the same as some tunes advertised in the forums) would not effect the warranty but I suspect that might depend on the dealer hiding the fact from GM if there was a failure that GM might blame the tune or delay the repairs. I also suspect buying the tune from the dealer would cost more. And even more again if acquired after the car was purchased or the dealer might not even offer it after sale if they see it primarily as an incentive to buy the car.So can this be done via ECM change at dealer?