Engine Mechanical problem
2002 Nissan Altima 4 cyl Front Wheel Drive Automatic 95005 miles
----------------------------------------------------------------
I REMOVED THE CAT CONVERTER, BUT THERE SEEMS TO ME NO DAMAGE VISIBLE. PLEASE ADVISE

The converter efficiency isn't alsway affected by if the bed is damaged or not, the precious metels inside it, platinum and paladium can be burned out of it, and you can't tell by looking at it, it is judged by how much switching is done by the downstream O2 sensor, and yours must be switching between rich and lean too much.