Possible Issues include failure to pass inspection and/or a fine for removal of federal mandated emissions equipment.

Functionally, nothing really if you have the carb tuned in good.

I had one removed once. Car was slightly louder and had a bit more rasp to it. Couldn't feel any performance change.

 

If your cat is plugged, failing or something along those lines you will notice it. Otherwise there isn't much of a gain unless you have some good flow going through there.

failing cat though then get that thing off there.

to me it's worth it though as long you don't have to do smog.