Are stock 1G catbacks 2.5"

[VIPERBLUELX]

My 91 GSX was basically stock when I got it, but I measured the catback and although it looks just like a factory catback it appears to be 2 1/2" starting just after the flange that bolts to the catalytic converter. Is this the stock one? If it's 2.5" then would it be ok to just replace the muffler with a high flow piece and be done with it?

 

[blackGSX2g]

I think the stock exhaust is just a hair smaller than 2.25''. You would know if it were aftermarket...stock exhausts are pressbent whereas aftermarket ones are usually mandrel bent. Also when you get a cat back exhaust, it almost always comes with a muffler, so I doubt someone would cut that off and put the stock one back on...though they may for the sleeper look, idk

In short, I'm pretty sure its stock. Did you measure just the outside, or did you take it of at the cat and actually measure the diamater inside the pipe?

 

[VIPERBLUELX]

I think the stock exhaust is just a hair smaller than 2.25''. You would know if it were aftermarket...stock exhausts are pressbent whereas aftermarket ones are usually mandrel bent. Also when you get a cat back exhaust, it almost always comes with a muffler, so I doubt someone would cut that off and put the stock one back on...though they may for the sleeper look, idk

In short, I'm pretty sure its stock. Did you measure just the outside, or did you take it of at the cat and actually measure the diamater inside the pipe?

I used a 2.5" die from our Bendpak pipe bender and it fit perfectly around the catback. I also connected a 2.5" downpipe to it and it's the same diameter.