Have you dealer asked you questions about your plenum? My guess is that and exhausts shouldn't affect the warranty. I had asked my dealer if a supercharge will affect things and they said if its concluded that it caused problems, then the warranty is altered. It's not exactly written in stones.

 

My dealer is not mod friendly. However, with that being said, they know the plenum is there, and have never questioned it. When I bring my car in, which is not very often, it always draws a crowd of dealership folks, because it's different and they want to know what I've done to it.

Lou