is the resonator something like a glass pack? Mine is damaged and I cant find a replacement.

its part of the pipe from back of the cat to the muffler

so if its one whole unit (cat/resonator) can I upgrade the cat and delete the resonator without having the exhaust sound louder?

try this GOERLICHS | A Full Line, World Class, Exhaust & Emissions Company

or this one to Maremont

Removing the res can make the exhaust very raspy. You can use a glass pack in it'* place.

Depending on your set up taking out the res can make it raspy like Dan said, however I took mine out and have dual GM Bosal mufflers and the only time it gets raspy is if I really hit it in park or neutral (when the engine is not under load)