New exhaust installed
 

Just took the first ride in my 90 GT since I replaced the stock exhaust with an o/r x-pipe, new O2 sensors, and a 2.5" Magnaflow SS exhaust. Even though the motor is stock, it sounds awesome! Just like I wanted, quiet at idle, comes alive over 2000 rpm's! The Magnaflow system was around $320 shipped from Brothers, great quality and a low agressive tone. At first the tips would not clear the GT rear bumper but a little work got both tips to line up nice.

One quick question. H-pipe vs. X-pipe:

H-pipe= cheaper, louder
X-Pipe=small horsepower increase (very very small)

Are the H's really THAT much louder than x's?

I have shorty headers and an offroad h-pipe and the Magnaflow SS catback. It's throaty at idle, not quiet like a stock Mustang. Whenever you tap the gas it comes alive, even at 1500 it has some decibles to the tone. It has a very nice sound to it though. I have contemplated about getting an x-pipe though, little more horsepower and little quieter like you said. ~Brian

The straight through design of magnaflow mufflers and an o/r x-pipe, will the loss of back pressure hurt low-end torque?

torque
 

No, you shouldn't lose any low end torque. Just keep your tailpipes on. Putting turn downs on can take away some low end torque. It definitely did when I tried that on my '90 GT.

Like Simi Stang said, you won't lose any torque, and the hp will climb a little bit. The x-pipe helps in getting the most out of a dual exhaust system. ~Brian

I wouldnt necessarily say its quieter, but it definately has a different sound. The H pipe has a raspier, old school muscle car sound, and the x has a cleaner more eaqualized sound.

Caymon

I've heard a guy with a stock type engine with an offroad x-pipe and Borla catback (very similar to Magnaflow) and I would say it's a notch quieter than my car. Maybe it's just because of the different tone though. ~Brian