Which cat should i cut off?

If you cut one off, keep it as you will be re-installing it for your next smog check!

But isnt a glasspack exhauat a cat?

No. You need the catalytic converters to pass smog. Just replace the muffler.

Tim, a glasspack is just a muffler and nothing more. If you live in a state that does vehicle emissions testing DO NOT REMOVE an of the catalytic converters. If you remove the rear cat you may still get a code. As Full_of_Regrets stated, just replace the muffler.

None! if you want it louder & more performance go to a muffler shop & have them make you a 3" single exhaust & Y pipe. Use 1, 3" inlet & outlet performance cat conv. & a 3" in & out performance muffler. I like Raven products. Glass packs sound cheap & suck.

Not a 3" then how about a 2" or 2 & 1/2" ? if it came with 2 cats, it needed them for emissions! Performace cats are bigger dia. inlet & outlet & low back pressure. More air in, & more gas exhaust out is my theory to make more hp. Bigger tubes give you more resonance, like the difference between a trumpet & a tuba sort off, understand? Glass packs use steel wool or fiberglass & blow out& rust eventully. They sound cheap to me like the people who use them dont really know about exhaust sound resonance. Expensive cars use Chambered Exhaust (still availible?) an option on my 69' SS L-88 427 Camaro. The pipe is crimped every 12' or so, like sausage, with a preforated baffle pipe in the center. The whole pipe front to back was a muffler & low back pressure for the best sounding exhaust sound. I'm an old school hot rodder & know, I even built my own tube headers. So I know exhausts.

Your best bet is to PROPERLY remove borne cats, use a pipe to beat the screens and packing out of them, essentially making them big exhaust pipes, reattach them PROPERLY and you won’t throw codes. Than, stop being a cheap ass and run two 2 chamber flow masters out the back. It will sound like a “truck”.