If you have a performance tune in your truck and return it to stock before going to the dealer. Can they find out you had the performance tune in and deny warranty service ?

It depends on the dealer. I have never had an issue but I am sure some members will tell you differently.

Every time we have called tech assit(techs at the dealer), the first question out of there mouth is does it have a tuner??, and we have to answer honestly because if it get ugly(blown engine, major repair that is not common) gm may come out and inspect the engine which does happen, and no one wants to get caught in a lie.....so use caution...

Every time we have called tech assit(techs at the dealer), the first question out of there mouth is does it have a tuner??, and we have to answer honestly because if it get ugly(blown engine, major repair that is not common) gm may come out and inspect the engine which does happen, and no one wants to get caught in a lie.....so use caution...
My answer is simple=Well I bought the truck from you(dealer) certified used/new with 28k on odo when it was less than 1yr old.Truck was from out of state(fe9) and supposedly another dealers managers personal truck.All I know is it came with nice exhaust,gauges,and a few other cool things.
Tuner? I have no idea what was done before I purchased it but you sold it to me all pretty like:D .And thats my story.
Honestly though,hope I never have to use it.I do know the truck saw some major mud time however as frame rails and cross members were packed with red clay mud that took me an entire weekend to clear out after I bought it.