Exhaust Flange Muffler Back Box Rusted Flange Clamp Repair for BMW E46 M3A common fault on E46 M3 models is failure of the exhaust flanges caused by rust corrosion of this part. Four flanges are used to clamp together and seal the intermediate pipe to the rear muffler backbox. These are constructed of cast iron (despite being fitted to a stainless steel exhaust) and inevitably deteriorate and split. These parts are integral to the intermediate pipe and rear muffler and are not available separately from BMW. The only option