Anyone know Holley Commander 950's? programming?

I would think the ground loop could be reduced by grounding the ecu at the engine (head w/O2, and good continuity exhaust to head). This should be done to keep the O2 ground voltage nearly the same as the ECU ground that is used for measuring the O2 voltage. The O2 output is very high impedance so you want to avoid any loading. The tab idea at the O2 and to the ECU ground point should help. I would not connect to chassis.

By not having a temperature sensor you are missing normal enrichments that need to happen for starting and warm-up. I would think this would require you to manually fiddle with settings to keep it running. O2 feedback is not a cure all for mixture control, especially narrow band. I can go into this more if you want me to ramble on.