Exhaust modifications and warranty

My Ford dealer tells me that if i change exhaust for an aftermarket one my drive train warranty will be void. The only exception is if i use a Ford Motorsport one. I have a 2001
GT, does anyone know anything about the Ford Motorsport exhaust. I was thinking about a BBK X pipe with cats and a MAC cat back system, keeping my original factory setup to put back on if i get problems later and need to warranty the motor or transmission. If i remove the rear springs and shocks can i get the factory exhaust out in one piece easily enough so i can store it just incase. I really want to put on aftermarket equipment because stock sounds so weak and feeble but i don't want to compromise my warranty. Any info will be appreciated.