I just purchased a a 2.25" G20 P11 stainless catback tubing kit $220.00 (included flanges and hangers). My P10 has a 2.25" VRS catback exhaust (they don't make a P11 exhaust) Mandrel Exhaust Systems or Tru Bendz as Krist mentioned does. I was also told by Mandrel Exhaust Systems that they make a full bolt up P11 catback with welded flanges and hangers MAGNAFLOW muffler and resonator for those who are interested.
I also picked up Thunderbolt 2.25" high flow spun stainless steel cat part#410225 39.99 It's a real cat with ceramic guts and from info I've gathered on different forums this type of cat converter out performs traditionally designed high flow converters. I also purchased a YONAKA 22" 2.25" stainless resonator $45.00 both cat and resonator purchased from Ebay. I preferred the kit in this instance for the P11.