Good question. Everything on this forum that is not OE voids the warranty. If that is your number one concern than i would stay with GM OE parts only. What I can tell you watch out for tuners who just buy Tunning software like HP and just start adding timing anywere to make power. AFR is key here. Tuning a car is not something you pick up overnight......Experance is paramount and should only be left in the hands of professionals. There are several very good tuners in the us and i would definitely ask around and make sure they no what there are doing.
This is one of many projects I have worked on.