hey, when i bought mine it had this code, there are two vacuum switches/sensors on the passenger side strut tower, i kept getting P0106, ended up running the vacuum sensor(the one with one hose) directly to the intake manifold, and bam, code went away. apparently the vacuum sensor is supposed to go through the "pressure switching valve"

so i guess that means my switching thing is bad, but my codes went away, ive been meaning to go to the junkyard and find another switching valve..

just a thought, hope it helps. good luck.