I got the exhaust on the Mustang, original setup was a 3 inch H into 3 inch Deltaflow mufflers, into 2.5 inch mandrel bent Flowmaster tailpipes.
I hated the resonance inside, so finally decided on Borla ProXS. Basically the same design as the Magnaflow and Ultraflows.
I tried to use a X pipe under the car, but I have the exhaust tucked up so tight, I really couldnt find a way to do it. I know Magnaflow does it, but mine is tucked up so high that you cant see the exhaust other than the headers. I wanted the same setup, and it wasnt easily done
It ended up being a muffler swap with some additional improvements
The guy that did the original exhaust also did an ugly reducer to the tailpipes, looked good from the outside, but it had a hellacious step on the inside. So I replaced the reducer with a nice gradual Hooker header reducer, about 6 inches long, and put a bolt on flange on the end of the muffler, now the H pipe and muffler assembly will drop out with 12 bolts, leaving the tailpipes hanging on the original hangers. Its pretty slick from a racing / repair standpoint.
FYI I did try to buy mandrel bent 3 inch tailpipes from Magnaflow but they wouldnt sell them seperately.
The end result was better than I expected, in 5th gear the car is quiet, idle is more quiet. Going through the gears it doesnt sound much different, more of a growl, cerrtainly sounds good, but it does feels "looser", my assumption is because of the better mufflers and the better transition into the tailpipes.
Most of all though, I listened to the radio AND could talk on the cell phone in 5th at 70 mph on the way home, something I couldnt do before, that was the goal
Next two steps are over the winter to ceramic coat the whole exhaust, Borla says no problem to stick the mufflers in a 600 degree oven, just dont coat the inside of the muffler.
I dig this quiet car deal, so I am going to lay down some sound deadener on the floor too. Its certainly more of a sleeper now.
Here are a couple links, second one is with the new mufflers, I'll do a better movie this weekend
Old exhaust - 3 inch H, 3 inch 3 chamber Flowmaster Deltaflow, into 2.5 tailpipes
http://media.putfile.com/489-FE-at-idle
New Exhaust - 3 inch H, 3 inch Borla ProXS, 2.5 inch tailpipes
http://media.putfile.com/Borla-ProXS-3-inch-with-H-pipe
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- 70 Fastback Mustang, 489 cid FE, TKO-600 5 speed, 3.70 9 inch
- 71 F100 shortbed 4x4, 397 cid FE, headers, Street Dominator, 280H, 5 lug Dana 60, 4 speed
