plugged cat???

Would a plugged catalytic converter give my xj the vibes? It shakes a bit under acceleration, no vibes when I let off the gas pedal. U joints on front and rear shaft are fine and motor mounts are ok. Catalytic coverter is the original one, I've never changed it the entire time I've owned my jeep (12+ years) and it's gotten it's fair share of dings from wheelin'.

any tips on diagnosing a plugged cat?

thanks
Dave

I've heard that you can bang on it and listen for a rattle (do this while it's cold). Mine didn't rattle but the previous owner had ignored the blowby issue and the entire intake was coated with oil, and the cat was pretty plugged. Before it was changed I ran Seafoam through the throttle body and it actually loosened up the cat a tiny bit as well. Still replaced it, but take that for what you paid for it.

I had a CAT that was fine when it was cold, but would plug up as soon as it got hot. The symptom was no power. Had a very hard time getting up 40mph or higher. Acted like it was running out of gas.

What about a tire balance issue.