1994 did not have a cat. The pipe size originally was 3 1/2 inches, and was until at least 1998.
Some 1994 had EGR systems, but no cat.

 

The 2nd gen down pipes were all 3" the cats were 4" out.

94's had cats if built after Jan1,no egr till 96.All EGR 2nd gens had cats
Federal trucks did not have egr,there are quite a few different pkgs availabe over the 2nd gen 12v's.Look at all the diff cpl's

Bob

 

Aha! I did not know that ANY 94 had cat. I stand corrected.

Muffler back was all 3 1/2 as far as I know, I guess thats what I was remembering from my old 94.
On my 94 the stock tailpipe had a "dent" in it to lower power to protect the Getrag automatic transmission.