X2 on the cat.....
Basically, with vehicle at normal operating temp, from a dead stop, lay into the gas pedal......if car revs out at 3K, and bogs down and doesn't shift, stop.....now LIGHTLY accelerate...if it shifts and slowly gets up to speed, it's the cat.....
Can verify by creating an exhaust leak before the cat(remove O2 sensor or loosen exhaust pipe....it will be noisy....just take a quick short trip....if hard accel is there, it's the cat....
Or you can attach a back pressure tester...rev to 2k...should not exceed 1.25 psi.....