what it says. I pulled the codes for the ses light and it said inefficient cat performance or something like that. Is there a possibility that this would cause some kind of vibration under acceleration? or should i look into other possibilities? Thanks
-Tony

I would look for a clogged or partially clogged cat to cause weak engine performance. Usually a car will be unable to rev very high due to the extreme restriction imposed by a clogged cat. Vibration is not what usually comes to mind when diagnosing a bad cat. Perhaps you could disconnect the exhaust from the cat-back to verify it's effect on the condition?

My brothers car ran like sh*t when his cat took a crap.