Hey there, anyone know the stock inlet size and outlet size at the muffler for a '01 Pontiac Firebird Formula? Thanks. I tried search but i never get good results using this search function on this MB.

 

I think it's 2.5 inches.

 

Yup^ 2.5.

 

Thank you

 

Stock exhaust diameter is actually between 2.25 & 2.5 inches.

 

Actually I just had a Muffler installed and the I pipe and tail pipes dia is 2 1/2 but necks down to 2 1/4 right at the muffler. The Flowmaster I had installed was 2 1/2 inlet and outlet. It was easy enough to just cut back on the pipe where it necks down.