A point to check is that the heaters in the lambda sensors have 12 volt power. Feed comes from the fuel pump relay so the voltage is only there when the engine is running. The fuel pump relay should be a single pole normally open relay, there are two output pins, the pump is wired to one pin and the lambda sensor heater to the other pin. If the wrong relay, such as a change over, is fitted the heaters will work when the engine is stopped, and turn off when the engine runs. ECU goes to limp mode and tends to be unhappy at idle. Found this fault on a Plus 8 where the service guys had changed the fuel pump relay.
