ecu reflash /remapping

Has anyone had there later model g6 ecu tuned ? Is there anybody out there reflashing them just chasing a bit more power from mine

As long as you have an injected engine which has fuel mixture controlled by a feedback system like an O2 sensor you aren't likely to find any way to get past the limits of the feedback loop. Richer mixture at the O2 sensor = fuel trim (pulse width) at the injectors. Depending on how many miles are on your engine, you might be further ahead getting the injectors cleaned and replacing the O2 sensor.