I think a plugged cat might throw a CEL, no? OP would have also noticed poor acceleration if the cat was plugged and possibly a rise in overall engine temperature.

Op says it has a CEL for the cat:

The cat can't throw a code directly though, I'm wondering if the mechanic is just assuming O2 code = cat, but depending on the code it might be the heater circuit or something.

@SupraTTturbo2jz do you have a list of the actual codes?

well i took my car to a diff mechanic, he took my intake off, the mass flow sensor, check to see if throttle body was actually cleaned, and checked all the plugs then cleared all the codes. my car has not been shutting off ever since.. maybe its just loose connections or bad sensor?

That's always a possibility, I've fixed quite a few things just by unplugging them and then plugging them back in. Usually I waste a ton of time in the middle though.