I just got a couple of hotdogs put into my system. For a year I had, 2.5" cat-back with a Xforce S12 twinloop. Since I was going on a road trip this weekend and the car was gonna be loaded, I anticipated that it was going to drone like it did on my drive to Sydney. The 2 extra resonators really REALLY make a difference. Each one is 12" long and 2.5" through so it doesn't affect the flow. The sound is perfect now, just a bit louder than stock and MINIMAL drone. best $150 I've spent. I've had all my exhaust done by Brian at Roadrunner Exhausts in Heidelberg West, Melbourne. X-Force S12 twinloop = $180 (From Ebay) 2.5" cat-back mild steel press bends = $250 (or was it $200, can't remember now) 2x Supercat 12" resonators = $150 Total = $580 And he's quoted me $400 to do some aftermarket extractors, which I will take him up on next month.