Help me build my exhaust for 2007 s/c GT

Greetings! I just picked up a 2007 mustang GT with paxton NOVI 2200SL supercharger running ~10psi and ~450whp.

The exhaust that came on it is too loud. It is straight piping (no cats) 2.5", turns into 3" after where the cats would be, to a couple glasspacks, then dumps downward onto ground before it gets to rear axle. No X or H pipe






So i'm thinking to either:

1) get a flowmaster axle-back exhaust, but only sold in 2.5" inlet size, so wouldn't the be bad to go 2.5" to 3" to 2.5" again? cut off the piping that turns downward and just continue back with custom 3" piping at the exhaust shop

2) get a flowmaster 3" cat-back exhaust that has an X pipe (loud but more performance)

3) get a maganflow 3" cat-back exhaust that has no X or H pipe (maybe slightly less performance, but may match my current tune best?)

The guy at Paxton said it will not need a re-tune if I change anything from the cat-back, but cat-foward requires retune. I think leaving the glasspacks and adding mufflers might sound best..but don't want to compromise power.

but I also wonder if removing the glasspacks and using mufflers might sound nearly the same. Just a tiny bit quieter....

Thank you!

LAVAgt2012 said:

I'd let the beast roar, invest in ear plugs

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my DD

The magnaflow (no X) and flowmaster (with X) 3" cat-backs are nearly the same price.

magnaflow: Magnaflow Cat Back on Mustang - YouTube (skip to 1:40)

flowmaster: Mustang GT's with Flowmaster American Thunder mufflers - YouTube (skip to 1:00)


the flowmaster definitely sounds meaner, louder, and raspier with the X-pipe. But then again they probably dont have their cats. The magnaflow videos i've heard generally sound softer and more "import-ish" in comparison. i think above video they have their cats intact.

very tough decision!

Red_LX said:

You sure there's no H in that system? It almost looks like there's a clamp between the two pipes in the first pic, as if there's a clamped together crossover there (like they do on some of the cheap H-pipes).

You will have drone regardless...however, a catted X or H, and some straight through mufflers, will keep it relatively tolerable. Mine is pretty good on the highway but sometimes headache-inducing around town.

Click to expand...

you sir.. just saved me 190 bucks for the 3" h pipe.... thanks. cell phone pic



im content with the 2.5" h pipe.... but i still have stock manifolds

PS i ordered the magnaflow magnapack 3" last night. One of the louder ones, the chambered magnaflow was almost like stock. Headers make it a bit too loud (headers, midpipe, and 3in catback). Bassani was too expensive but good. American thunder was too raspy and obnoxious. Borla sounded good.

edit: looks a bit rusty... do you think an SS 3" h-pipe splice would be worth it?