Wiggle, wiggle, wiggle wires on Furnace Pressure Switch makes it work -- should I replace Switch?
It could be the connection or the sensor.

If those connectors move a lot when you wiggle them, they may just be loose, and vibrations from the furnace affecting them.  So the first thing I would try is pulling the connectors off and squeezing them a little bit with a pair of pliers, so they dig in a little tighter when you put them back on.  That costs nothing, so its worth a try.