94 Camaro - reason for failing smog emissions?

I took my Camaro in to get smogged this weekend, and it passed everything except the Nitrous Oxide at 25 mph (it passed at 15 mph). The max allowable is about 700 ppm, and my car was about 1,200 ppm. Is there something that is common on 1994 Camaros that could cause it to fail this? If not, what are the most likely things that could cause this? Thanks. :)

How old is your catalytic converter? It might be getting old and inefficient.

It might be the original cat (my Camaro has over 180,000 miles on it), but I'm not the original owner, so I'm not sure. We were thinking that might be it, but I was just wondering if there were other possibilities as well.

One way to check, is to get under the car and look at it. If there are no weld marks on the back side of the cat to the I-pipe then its original.

You'll more than likely need a new one. They are expensive but its one of the only ways pass, without finding a shop that you can pay off or something like that.