Picked up these off market place today. Twin 2.5 going into 3 inch and herrod mufflers. I'm not sure if this has been cobbled together by a backyard dude or not but they were a bargain and hard to pass up. I really really want to keep the car as stealth as possible while being as powerful as possible so I'm not 100% sure I will be using these. Perhaps a test fit and drive to see how they go sound wise. The guy sent me video clips and it was crackling on decel after a rev at idle and sounded absolutely terrible - he later said he modified the car with no tune at all and the engine blew up - wonder why. Question is, is there any performance gain from these pipes? I mean at this stage the car has good induction, cold and hot side piping and will shortly have a modified 3582 turbo. Once the turbo is fitted and going back for a touch up tune, will I see more kW with this 'cat back' style arrangement or purely just extra noise.