[TampaTundra]

If you do an exhaust properly it will give you better performance and sound along with better mileage. And there are many mufflers and cat back systems with little to none cabin drone.

You lose back pressure when A) you put a muffler on that is too big and does not provide enough back pressure or is too small and has so much back pressure that the exhaust can not flow through it. B) you use pipes that are either or both, too large in diameter or are kinked and not smoothy mandrel bent.

There are a good number of exhaust for the 07-08 4.7, just look one up you like then buy the muffler on its own. Or you may be able to find the cat-back kit on ebay for the price of the muffler and installation.