When i bought my brand new gsa in Jan this year, i asked my dealer that very question. He said as long as the part does not cause anything else in the area it has been fitted to to fail or get damaged, there should be no problem.
So i asked if i get a fender extender for the front wheel, and the cylinder head paint starts to peal, you aint going to come back and say no warranty as i have modified it are you?
He said no, that would not happen, but he said if the front mud guard cracks where i have drilled for the extender, then it aint covered!
Kr
Craig