Crazy Coding 2003 GMC Yukon 5.3L non-flex

Back in November I brought my 2003 Yukon SLT 5.3L non flex fuel for inspection. It passed the safety but it had a code. Knock sensors both 1 and 2. I replaced the two sensors and the code went away. After that it coded P0101 my MAF sensor, replaced 5 times and finally got rid of that code. During the MAF issues I was also getting the running rich bank 1 and 2. Replaced the MAP sensor and the rich code went away but started getting the Knock sensor 1 and 2 code back again and now the rich bank 1 and 2. I've driven over 6000 miles. the intake is OK no leaks. I replaced the Exhaust manifolds and gaskets. new spark plug wires 8MM new coils MDS high output coils and new plugs. replaced the electrical plug on the MAF. Could it be the ECU ?
I had the fuel rail pressure checked and they said it was OK.
I took it out after clearing codes drove it about 45 miles and now I got a code for 1 O2 sensor not operating. The thing that gets me is the truck is running great has lots of power and the mileage is good, idles fine. The codes just seem to be coming up at random, sometimes it's just knock sensor bank 1. another time it codes both knock sensors. another time I'll get no knock senor but both banks running rich. fortunately the MAF has not returned. Note: I did have the truck running on hydrogen about 3 years ago and had a controller that was sending false info to ECU, like instead of water temp at 196, I would send 205, changed the Map info, the 02 sensors was sending false info to ecu . could all that have caused problems in the ecu?