[kilroypr]

The Boost meter just shows you positive pressure applied to the intake air entering the engine. IF the SC is working properly it would not affect your idling or normal car operation. When hard starting your car the meter could show a couple of ticks but that is normal. The input for this gage comes from the PCM itself no special sensor out there.
IF you install a Mechanical Boost gauge then on top of the SC there is a small valve that has positive and negative boost depending on driving conditions.
But this valve has nothing to do with the OEM gauge you have on the trip computer. And has nothing to do with hard starting.
Do you have spark on the plugs? Do you have enought flue arriving to the Fuel Injectors?
Looks like you have a fuel delivery problem. The MAF and O2 sensor control the Air/FUel Mixture and determines how rich or lean it will be depending on car driving conditions. If any of these sensors are not working properly or the Fuel Pump is not delivering enought fuel then you might have the problems you are describing there...