I agree with you. One reason I haven't really modded mine (engine-wise) is all this crap some of you are dealing with regarding mail-order tuning, etc. It is BS. There is _no_ excuse. Even if the product development is good, it is extremely poor product support (same can be said for Borla with these tips).
This is the only vehicle I've ever owned that has remained this close to stock after 15 months of ownership. Springs, cat-back, wheels. So far that's it. As a hot-rodder, I don't even consider those "mods." LOL
I wish the trusted, local GM shop worked on these.
Sorry you are having issues... and I hope other owners are indeed listening to the problems dedicated guys like you are having, instead of throwing more money at these vendors/manufacturers.