My next upgrades r probrably going to be Exhaust and intercoolers.
But i'm really set on a Quad set of pipes for my 2001 S4, I've SEEN it before, but i cant seem to find it anywhere any direction would be great!

 

hay sorry i wish i could help i have seen it as well on sites but no company sells it i believe it is all custom work. My buddy did the same thing to his v6 mustang. most shops could prob do it.

 

I just did a full custom dual exhaust on my '01 and was set on the quad exhaust as well. To be honest with you, there really isn't enough room to do it properly. You can't pass any tubes on the passenger side of the car so the only option is going to the back and then running across inside the rear bumper and out. basically, on the muffler, you'd need a dual exit and you'd put dual tips on each exit. But apart from the look, it's pretty pointless and you're adding work and weight for nothing. You guys probably saw it on an avant...there's a thread on AW about it, I think.

Good luck with the exhaust.