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Fitted the ZZP 2.5" cat back system last night. It fits the 5.3L V8 for length and flange connection location just fine. The main problem I had was getting the mufflers and tips located in the centers of the cut-outs. It's got a good sound but a little more 'drone' than I was expecting.

Anyone know if they mellow with time? I've read there is a break-in period but imagine it will only get louder, not quieter. Overall though pretty happy with the system for the money.