Anyone know, I've gone through over 200 threads, no specific answer?
I'm looking to by a universal fit but not sure if it's 2.25, 2.5, or 2.75?

 

Take tape measure and wrap it around the "Y" pipe where it enters the CAT. My '93 measures 9 and7/16" in circumference = roughly 2 and 15/16" diameter. Hopes this helps! A lot easier to measure with a tape now than curse it later. My new Random Cat measures 9 and 15/16" outside circumference and 9 and 3/8" inside circumference. This is going to be a problem for me with both pipes the same size and the same length of the CATs.