Check this out,
Pinscher
That's ~72mm O.D. for the OE tips, ~54mm for the pipe exiting the back of the muffler. Keep in mind the OE muffler has "rolled tips" so the internal diameter is significantly less. Not that it matters if I understand you correctly.
That's ~75mm O.D. for the Performance tips, and ~54mm for the pipe exiting the back of the muffler. The PE does not have rolled tips so the internal diameter in the tips is probably 73mm.
The pipe coming into the back of both mufflers is 63.5mm O.D.
For new exhaust tips, you ought to be able to use Vibrant 1164 2 1/4" band clamps -
https://www.amazon.com/gp/product/B0...=ATVPDKIKX0DER though I have not personally verified this - I did buy the 2" model, the 1163, and it was just barely too small. The 1164 is the next size up but I haven't ordered a pair of them yet.
I have the E92/3 Performance Exhaust installed on my E90, so my tips stick out comically past my bumper. It's starting to grow on me
Hope this helps.