BJ is right, the after market exausts do nothing for peformance unless you have gobs of power and use it.the only aftermarket exausts that do what they are supposed to is the replacement ones not the so called upgrades.
Yes your muffler is covered by the warrenty,for 75k in fact. the entire emissions system is due to the govt. stepping in and making the car companies do it.

out of all the jeeps in this town the d**n gremlin had to invade mine

I've done so much,with so little for so long i can practicly do anything with nothing