Thanks for the reply Jeff. The exhaust was never as quiet as a Toyota or Honda but the new two piece exhaust system seems noisier than the original one peice system.
My only concern is that the cat was damaged but there is no indication that that happened. The car gets over 4K on a quart of oil and the economy and performance are excellent. I'm just going to forget about it.
As an aside, the exhaust system is the first and only repair item I've had with this car. Other than Mobil 1 in the drive train, all parts and fluids have been M-B and I've still spent less than $200/year for maintenance including V-rated Continental and Pirelli tires and M-B batteries.