I have the wrong rear muffler box on

[aabdelhamid]

my M20 520i 1990. I just figured that the rear muffler box is coming etither from and E30 or a 518 E34. It is simply minute and I am planning to change it and put in the fat 520i box, is running the new one going to differ in terms of performance and what are the expected issues from running the one I have now???

[e34bim]

the 520i has a pipe diameter of 50mm any less will be restrictive and give a rasp sound like a fart "bigger is better for the sound alone" and gets the gasses out quicker