Standard exhaust on a WRX
 

HI,can anyone confirm that the standard exhaust on a 2002 WRX is 2.5".Thanks

yes (ish).
Most European spec after market exhausts will mate up OK to a standard 2.5" system.
ALot of Jap Spec aftermarket exhaust do not as they tend to be larger bore and also replace the flange joints with sleeve joints.

most downpipes are 3" reducing to 2.5" at the bottom to mate to a standard or aftermarket 2.5" system.

Thanks Scott,will purchase the sports cat I mentioned.De-cat up.pipe should arrive this week.