The shop that made my quad catback exhaust for my Hartge diffuser is thinking about making about 10-15 setups. This is a feeler, and he want's to see just how many people will be interested in the quad setup. The pipes will be made out of stainless steel, and will be made to fit the Hartge diffuser.
Now onto the price, he is asking around 400-500$ for a;
1. Stainless steel 3inch piping with a true quad setup (made to fit Hartge diffuser).
2. The quad setup can be made with any exhaust tips, such as stainless, black, titanium burnt (costs extra).
3. The quad setup will be a straight pipe setup, resonator, mufflers will cost extra.
If your interested, please post on this thread. If we have enough buyers for this exhaust, it's a possibility to have a group buy discount. Location is in Orange County, California, but he is willing to ship it. Build time will probably be around 5 days to a week to have an exhaust made.
If you have anymore questions, feel free to PM me, thank you.
-W
*Disclaimer : I am not the owner of the exhaust shop nor do i work for him. I am simply helping out the 1er community since the aftermarket scene is limited 
.*