Catalytic Converter, legalities Options

[Red_06_EvoRS]

I've been hearing ugly rattle/vibrations since the summer on my 93 GSX. I got out and listened and it sounded like it was coming from the catalytic converter area. It only does it when idling slow or chugging from a dead stop. I finally took it to a local shop and they said that I need a new catalytic converter (a couple of heat shields could also use some work).

I've always had in the back of my mind possibly putting on a larger exhaust, etc. etc. I know replacing the catalytic converter for no good reason is supposed to be illegal. So my question is, if I'm going to have to replace it anyway, is it legal to put in a larger/higher flowing one? Or does the stock one do the job well enough not to worry about it? I could see where the feds might say that if it's not replaced with an exact replica that it's not guaranteed to handle the smog duties that it's meant for. Anyone know?

[Red_06_EvoRS]

I took my car into Meineke (in Bloomington) for a second opinion this morning. I've had good luck with them in the past and I figured it can't hurt plus they always let you go out into the shop and actually see what they're talking about with it up on the lift.

They said that it was just the heat shields as I had always suspected. They took them off and charged me $5. The rattles are now gone.

Neil Tire & Auto was going to charge me over $300 for the cat & heat shields. The thing is I've not had a problem with them in the past with tires.