Real GTS mufflers don't have the final baffle inside (a tack-welded washer on each output pipe). The noise level is a couple of dB higher than std mufflers, as is the gas flow from the 2-1/4" header pipe. Some guys run 2 big Supertrapps, some run 4 small ones on u-bends, some run Flowmaster mufflers, and Edelbrock came out with a muffler thats the correct size. Your very own dB meter from Radio Shack only costs $37, and will last the rest of your life. Get one and start checking; note the sound level inside the car is very different from that outside. Find a baseline sound level you like and go from there.
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