Ive heard the SLP isnt terribly loud but the slp loudmouth one is. then again "LOUD" is a relative term. what you think is loud might be quiet to somoene else.
The biggest complaint ive heard is problems with drone inside the car.
Try to find someone with the new GM performance pars exhaust. Its a perf exhaust but since its made by GM Id tend to think it was a bit more tame without the drone.
Justa thought.
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2000 GTP Coupe traded for a 2004 GTO