Maybe this has been done, but I haven't seen it and thought you might find it interesting.
We do something similar on the Z06 Corvettes all the time.
I had Corsa mufflers with the stock manifolds and thought it sounded pretty good.
We dynoed the car at around 620 and 640 torque, so it was starting to get pretty loud at WOT, but not obnoxious.
I put a set of American Racing Headers on it and OMG! It was absolutely stupid loud. I never even drove it out of the bay.
I put on a stock muffler but now it's too quiet. I will say, however, that the stock muffler sounds pretty good with the headers. It's just too quiet.
So today we fixed it.
We cut the muffler open and removed all the glass packing. There is a HUGE amount of that stuff in there. The internals of the muffler are actually made from straight through 3" pipe. It's bigger inside than a Z06 muffler. I was surprised to see that.
There is nothing in the pipe to interupt the exhaust flow and there is no reason it won't flow as well as any aftermarket muffler.
The pipe has multiple areas where it is full of perforations to allow the sound waves to pass into the glass packing. We welded sections of pipe over a little over half of the perforated area. 
I'll test it in the morning and see if it needs more holes to be covered.








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