Right, just had a milltek centre pipe fitted with a 200cell sports cat and had a downpipe made up. But with the down pipe the flexi was moved to just befor the cat on the horizontal rather than standard it is on the vertical. Now i can get a knock and a vibration which can be felt through the seats and the gear shifter. Do you guys think the flexi either needs to be on the upright where it is standard or the cat needs hangers put on?? Any views welcome.