I tried the Gemballa and sausage-style Dansk and both had the resonance with my car that drove me nuts. I am quite pleased with the Dansk Sport muffler that I finally got that looks like the OEM Porsche muffler but has a higher flow rate.
It can be a little raspy, but does have a deeper tone and there is no resonance. For what its worth, putting headers and high-flow cats on the car do make for more resonance, you can hear it trying to come through even with the stock muffler.
Ed
