Here's the exhaust setup on the current 944 turbo.  If you want super high-flow capabilities with the minimum of noise level, this is it.

The system consists of the Speed Force Racing 3" ID, mandrel bent, exhaust system.  This system runs all the way to the turbo. 

To quiet the system down without loosing power or causing additional back pressure, we installed (3) Borla XR-1 stainless steel race mufflers.  These are straight through mufflers, and being that they are 3" ID in and 3" ID out, they are big enough to put your arm in them!

The mufflers consist of (1) 12" round Borla XR-1 where the cat resides, then a (1) 12" oval Borla XR-1 next to the transaxle, and finally, (1) 16" oval Borla XR-1 in the stock muffler location.

These mufflers are light and durable and are the best on the market.  The sound is very very deep and low, thus giving no real indication of the awesome power this car produces! :-)

People told me that, "you'll never get a 3" exhaust quiet".. well I guess they were wrong!