Inactive O2's? ls7.

Hope someone can help with this. I'm working my way round Efi Live and have done a number of scans and also tried several tunes I've been helpfully provided with.

The lambda's don't fire up, not a trace. I even replaced them with new one's. On just one occasion they lit up upon engine start and then switched off. The heater wires are live. Basically the car fire's up great but I can't get past a really lumpy idle that will stall if I rev the throttle. I can hear the air entering the TB but the fuel's not arriving on time. With DVT I can get a decent idle and also a decent throttle response.

I've found the various lambda settings but am not sure if they're correct. Can anyone suggest 'settings' for a stock ls7 engine that should put me in the right zone please? Until I get the lambda's working I can't progress. It's as if I need to find the 'On' switch.

Specs are, stock 'stand alone' engine, no CATS just a muffler on each bank. The lambda's are fitted into the end of a cast factory header just after the rear cylinder.