Originally Posted by Desmo748
I think it has be answered (in numerous post) that cat back will not void the warranty unless they can some how place the problem on the modification you did.... but i don't see how even the most unscrupulous dealer can pull that off.
That and obviously they won't work on the modified exhaust. Unless it's a Ford Racing product that was installed by them.
People have occasionally run into dealers that won't work on your car at all if it's been modified; even if you only have basic bolt-ons. However, that's pretty rare. Some are just overly cautious and clearly have been burnt before. Can't say I blame them.
Just check with your dealer first if you are unsure.