Turboplus
The only thing that the Volvo turboplus does is increasing the turbocharging pressure at full throttle. At less than full throttle the system is not active, hence it can have no effect on starting.
A faulty lambda sonde will have no effect on starting either, as the ECM only starts to fine-tune the mixture after it receives a stable lambda signal. During starting and picking up the combustion air flow is too low and too cold for the sensor to work properly. I am fairly sure the mixture is set according a fixed strategy based on temperature only and it will start even with a disconnected sensor.
Only in the old carburettor days pumping the accelerator would enrich the mixture, as injection systems do not have an acceleration pump function. The only information the ECM gets about the position of the throttle is from the throttle position switch (TPS). This is either open or closed, nothing proportionally, so there is no way the ECM knows that you are pumping the pedal. The ECM only gets indirect information from your foot on the accelerator via the AMM, not from the throttle pedal position.
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