Some of these cars have 2 sets of cats, you may see the precats up front by the exhaust manifolds. To check for restricted exhaust, just loosen the pipes at the manifolds.
You could also be dumping fuel into the exhaust, like by a misfire on a couple cylinders. Does it idle OK, or does it miss? The raw fuel dumping could cause the cherry red cats.
Another reason I've seen for a misfire like this is a broken ignition rotor bracket, throws the timing way off but surprisingly the thing'll actually run.
If none of this pans out (or maybe even before trying some of these suggestions) you could do a quick compression check.

Gilly