Simple really, the aftermarket boxes are just that, something that fits but does not really MATCH the original design requirements, i.e. size of internal pipes and exactly the same construction.
Had a similar problem a few years ago when the company car leasing company insisted (for £ reasons) that an aftermarket final box had to be fitted. It was awful, after a bit of argy bargy they agreed to have the MGR parts fitted, all was returned to normal silence.
|