I was checking out TRD parts and accessories, and I came across the TRD headers and Borla exhaust. I've seen a lot of you guys with upgraded exhaust systems. If I'm going for the HP gain and mileage gain, then wouldn't it make sense to upgrade the headers? Is there any sense in upgrading the muffler if I don't upgrade the headers?
My thought is that the factory exhaust manifold is more restrictive than any muffler would be, even the factory muffler. Any thoughts on this?