Some dealer are a pain in the a$$ when it comes to aftermarket parts. I'm waiting to take my car for the free oil change with the Custom Air Intakes ans the F.I. Catback installled.
They have told me Hall Nissan are real pricks when it comes time to aftermarket parts!
However, just mention to them
The Magnuson-Moss Warranty Act. A lot of service managers are clueless.
http://en.wikipedia.org/wiki/Magnuson-Moss_Warranty_Act