sorry, no time to read back through the build thread.
when you did the wiring did you send the ecm out for reprogramming? otherwise if you delete the cats you need to fool the ecm so it doesn't read false o2 sensor readings. there is an upstream and a downstream o2 sensor, one ahead and one behind the cats, and the ecm checks one against the other to read how efficient the cats are and thus how efficient the fuel is being burned.
some sensor checks
https://easyautodiagnostics.com/gm/4...e-maf-sensor-1
https://www.autozone.com/repairguide...96b43f80cb13f9