Crystal Marie Ormsby

So I have a 2011 Chevy equinox and about 3 weeks ago it pulled a p0420 code. I took it to the shop and had it tested, needed a new cat. So we replaced that and o2 sensors and cleared the code. Now the code is poping up again and we hooked it up and everything is running fine on the scanners. Although now when I go to take off I press on the gas pedal and the car doesn't accelerate. We've checked everything possible that would cause this and still haven't found a fix.... Any ideas?