If you bring your car to the dealer and he just suspects that your aftermarket gadget is the cause of the problem - you have given him enough ammunition to say 'NO' to warranty coverage. It is sometimes hard enough to get legit coverage!! Too many people jack around with their car - something goes wrong and then they cry to the dealer 'I want this fixed under warranty'. Just because you install an aftermarket part successfully does NOT mean it will always be working. Case in point: a woman I know put in some aftermarket seat heaters in her Miata [which is still under warranty] they worked great for the first few weeks- but then...the damn seat started to toast up and actually burn while she was driving!! Luckily she was able to pull over and splash some water on it and yank out the fuse. Her beautiful tan leather seat was ruined. She actually had the nerve to go back to Mazda to have the seat replaced under warranty!! The dealer promptly told her 'NO'. You want the seat..you buy it. Moral of the story - expect a possible 'NO' when you tamper with aftermarket stuff.