I changed all the vacuum lines this afternoon, took off the N75 valve, reads 27 ohms which seems like normal, clicks when energized..but..it had oil residues in it, so I sprayed some cleaning solvent through it, blew it out, and noticed the click sound changed when I energized it..I shook it and noticed it may a click sound, which only happened once. sprayed some more solvent through it, then some penetrating oil, blew it out and shook some more...now it rattles more consistently when I shake it, but occasionally seems to stick...The limp mode seems to correlate to a boost spike so I am thinking I may have a sticky N75 valve...I read a post about someone disassembling one, I have a buddy with a spare so that is what I am going to do next.