Stebro Cat resonator

I just got my Cat Pipe from Stebro for my 1988 328 and both ends are larger then the Stock and it is also 1/2"longer,there are no pipes on one end to support the gasket for assy. the stock has a 2.750" DIA the stebro is 2.874 inside DIA so i need to make up one pipe for one end and a nother to make up the diff from 2.750-2.874 otherwise the gasket will collaps in assy.is this normal ?the packing slip says" Euro resinator' I ordert US style is there a diff? i try to line it up but my muffler will shift a good 1/2" to the left so my Tips wont line up with the grill.big Mess.i dont know wy the all tell you exact the same just bolt on,i think i have to take it to a muffler shop and get it cut and reflaired so i have the right lengt and make some pipes so the gasket has some support.did anyone had the same problem.

 

Stebro just called me and the think i got the wrong one very nice people so the will send a new one asap no harm done but i still like to know the diff from Euro to US .