I recently got bored at home during this crappy winter season and decided to tinker around with my 2001. I had a flowmaster cat back system, rear exit that I decided was too quiet. I decided to measure out the dimensions of the muffler and went to work fabricating a "y" pipe to replace the muffler. After measuring, cutting, and welding I had a pretty darn good looking y pipe to install! After getting the muffler off, I bolted up the new pipe and it fit perfectly. Took me about 20 minutes to install, not including pipe fabrication of course! So now I have a straight thru design with duals retained from the flowmaster system exiting out the back, pretty cool. I started her up and man alive! It sounded kick a**! It actually sounds like an older muscle car, on the loud side and throaty. The cats muffle the sound just enough and with the duals out the back its still relatively quiet in the cab. Power wise, i'd say there is no gains or losses. It performs about the same as when I had the flowmaster muffler on it. I'm much happier now that I can bark at all the loud Chevys and Dodges out there instead of whispering!
If anyones interested in a pipe like this, I can fabricate it for you. I'll try to post some pictures and some sound bytes later.