I have a used resonated x-pipe from Fabspeed that was on my M3
It currently has stock cats (included in price) clamped to them which means there is no modification needed for install. It will bolt right up with no cutting your stock system!
New they are $795 plus shipping.
My price: $475 with free install at IND.
If interested please PM or email me at Thejesal@gmail.com