i just fitted a new box to my jetex and the only trouble i have had was it kept droppin one side but that was due to the joint at the 6 branch to my de cat .... u cant get any slincers round the wrong way as they are ediot proof ...i`ve had to use a spacer sleeve on mine to go from the decat to the system jaut make sure they are using stainless clamps as if u use standard ones the react with the stainless and rust and break very quickly ..... sounds like its knockin on the rear axle which i had just moved the system foward by pushin the de cat into the system more