57mm or 63mm

[carlo_sg]

Unfortunately where I live we cannot get Brand name exhausts, so will be having a custom free-flow exhaust made.

I've currently got a RS Tuning map and performance panel filter.
Should I go for 57mm or 63mm tubing.
The system will be a copy of the popular exhaust kits available, with one center box, and two rear boxes.

Thanks!

 

[CraigAPD]

63mm or 2.5"