P0430 and P0420 Codes with no repair luck

Got P0430 and P0420 codes show up for inefficient cat. Replaced post cat O2 sensors with no luck; Check Engine light came back. Took to a Chevrolet dealer who said cat needed replacement; doubtful they went through all many perpetrator problems first. They replaced the cat; two days later got a MAP code (P0106), then again P0430 and P0430. Changed the MAP to no avail. Took back to the dealership. They replaced the two new NTK post cat O2 sensors and went through compression tests, anti-freeze pressure test, ran scan tool to check all sensors, did a smoke test, checked fuel trims. Said those were good. They replaced the cat again. One day back, CE light back on and more P0430 and P0430. Truck seems to bounce back and forth roughly when AFM kicks in between 30-20 MPH when slowing down. That goes away when truck is run in L5 to cut AFM out. At my wits end. Do you think this might be a bad PCM?