I currently run BB 3in catless from the turbo on my SRT-4 and I can say the sound is by far better than I have heard on any other system. Cant say for the sound on an N54/N55, but I can attest to the quality of the work, I have had the system on my car for nearly 5 years no with no rust, and no leaks or broken hangers etc. Great product to buy from Billy Boat! Here is a sound clip...
Full motor build
Before the motor was built...
If I wasnt looking for a quad tip setup, id be all over this... Any plans for a quad?