did some searching couldn't find anything so here goes:

Stock cat is really getting on my nerves now with its rattling and smell when I'm driving the car "my way" so right now I'm a little to poor to have a high flow cat put on at the garage so I'm thinking I'll just cut the @!#$-er down and replace it myself with a straight pipe with swelled ends and a couple of clamps.

I just need to know what is the size of that exhaust pipe before I cuts down the cat. I'd like to have the right size with me when I does this rather then have to drive my car somewhere with my exhaust opened up to pick something up! lol

If the bird's are the same as the cavy's then your should be 2"...

'88-'90 V6 Z24's all had 2.25" pipe with a dual outlet turbo muffler stock
'91-'94 V6 Z24's all had 2" pipe with a dual outlet turbo muffler stock

i have just changed my cat because the damn baffles were broke and were making a sound like the exhaust was rattling on a heat sheild. well if you just straight pipe it it prob will not pass emissions and dont buy a straight thru cat cause they wont pass either so just buy a high flow so it will pass haha or less you dont need emmisions or inspection like we do here in Pa