Engine misfire

Recently I took my 2005 yukon 5.3l into the local dealership because the CEL came on. The engine had no power when accelerating and idle was very rough. There is also some knocking and pinging when accelerating. Also the air conditioning switches from cold to hot on its own. At the GM dealership the found a p0300, and p0332 code. They preformed the following service: 1. Injector cleaning 2. Replaced and reprogrammed ECM 3. Replaced knock sensor 4. Replaced all spark plugs. Unfortunately, the CEL came back on. Now I have p0101, p0300, and p0420 codes present. When I took it back to the dealership they told me I had a bad mass air flow sensor and need to replace the catalyst converter. I replaced the mass air flow with a new one. I also had the catalyst converter system checked out by another shop and it is working properly. But vehicle is nearly undrivable due to the poor acceleration and the CEL still stays on. Any ideas what the problem and possible fix could be?