Sometime this month im going into the shop to get a full custom exhaust. i need some suggestions on what High-Flow Cat and what kind of muffler to get. Im leaning towards a Magnaflow cat but i dont know which to get. I want to get a good hp gain that i can feel and i dont want a LOUD exhaust considering my engine is stockkkkk for now.
and for a muffler i want something round. but iam open to some oval shaped mufflers.

 

hard to get a HP gain and quiet... I used Magnaflow cats and factory resonators. Not too loud.. I plan getting high-flow resonators.

 

what model cat did u get?

 

Magnaflow's highest flowing cat is a metal substrate unit: model number 5995x. I believe 59955 is the 2.25" inlet/outlet style. The flow is 10-20% better than the standard ceramic Magnaflow cat, and the cost is about double.

As for sound, generally good flowing exhaust items present fewer sound wave deflection opportunities: meaning the exhaust will get louder by nature. I know Gibson make some universal exhaust mufflers that are generally about as quiet as any on the market that still flow enough to be considered a performance exhaust.

Ultimately, swapping the cats and the muffs is not going to give you a big performance gain. The primary motivation for doing such an exhaust surgery should be for sound since the stock exhaust is pretty well designed.

The stock cats are metal substrate already. The mufflers are straight through in design. Significant power gains (more than 5hp) can only be had from the exhaust by way of headers. If you want butt dyno power without a big increase in sound, I would spend my money on some S&S Headers and adapt the stock exhaust to the headers.