Audi A4 2.0 TFSI 2WD B7 cat-back system
I highly recommend Milltek exhausts, an Audi technician told me that it's the nicest sounding exhaust for these cars.
Milltek Sport have released a cat-back system for the 2005 onwards B7 model of the Audi A4 2.0 FSI Turbo (front wheel drive / frontrac).

The cat-back system consists of a connecting pipe, centre silencer, left-hand and right-hand rear silencers, and dual 100mm (4") tailpipes. The larger-than-standard tailpipes fit the cutouts in the rear bumper more closely and enhance the look of the rear of the car whilst remaining true to the original design. It's classic Milltek - genuine performance enhancement, sounds that are truly awesome, looks that are subtle but sexy and a feeling of true exhilaration.