Bob,

1-4-2 in A3 = "Faulty Stop Light Switch, open or short circuit"
probably intermittent, check if your brake lights works and if it does,
clear the code.

4-1-1 in A2: The throttle position sensor is a potentiometer attached to
the throttle shaft in the throttle housing. The unit send a linear signal
to both fuel & ignition system ECUs proportional to throttle opening.
... No direct relation with the PNP switch but it might explain the
"bucking", the ECUs doesn't "know" the throttle position and transmit
bad ignition timing and/or fuel mixture informations to the engine.