Does anyone know what a decent air fuel ratio is for a 6G72 is. Possibly someone with a unichip or emanage? what was it tuned too?

During idle and low to moderate throttle openings it runs at stoichiometric which is 14.7 to 1. This is under the control of the ECU and oxygen sensor and runs in a feedback (closed loop) mode. At wider throttle openings it goes into open loop mode and runs richer according to factory mixture maps, for more power and keeping the burn temp down.
Hope this helps.

should be more around 12.6/13

I believe closed loop is when the the engine is running to its mapping and open loop is running from o2 sensor readings.Closed loop comes in above a ??% throttle usage etc.,