I've heard a 4.6 w/magnaflows on it and it was still as quiet as stock, if not a hair more quiet. You'd have to have an off-road h or x-pipe to get any sound from it. On mine I just removed the mufflers and tailpipes, then added turndowns on the stock H-pipe that dump off in front of the rear axle (welded to the stock muffler hangers). It sounds quite good, too. Not overly loud at all. It's amazing how much muffling those 6 freakin' cats do. No drone at 2000 rpm like most mufflers/catbacks (flowmasters, etc.). You can hear the car, expecially when ya get on it, but at idle it's actually pretty quite with a nice low rumble to it. I love it cause it doesn't sound like any other stang around here. I get alot of compliments on it. Try it and see how you like it. It's very cheap. Cost me $30 to have a shop do it. What could it hurt? You want to get rid of those "50 pound" stock/crap mufflers anyways, don't you? You still have plenty of backpressure from stock h-pipe so I would not worry about that.
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1996 Mustang GTS: 5-speed, K&N, removed air silencer, 3.73s, turndowns after stock H-pipe (no mufflers)
[This message has been edited by 96GTS (edited 07-18-2000).]