^ I've drove one of them for an extended period once... bits of trim were falling out and it had 35k miles on it. :-p

I work on cars including exhaust at work.

you won't gain anything by changing the pipes. the caravan/t&c pipes are plenty big. you MIGHT gain something from free-er flowing mufflers.

as stated, cars are designed by expert engineers...the same engineers that put half chryslers lineup battery in the d^&* wheel well and the steering rack wedged behind the engine to name a few expert designs. goal #1: cheap. goal #2: emissions (mostly manifold/cat) goal #3 of exhaust: quiet (depending on the application)goal.

the biggest FE gains are in FE oriented headers and cat followed by free flowing muffler.

I would think that any gains (FE or otherwise) would be negated by the weight of the 2nd set of pipes and the 2nd muffler.

Personally, I'd use the $90 for something else.