The big deal isn't with the switch itself, but how your GEM is programmed. The GEM gets a resitance reading from the switch and acts accordingly (engages 4H, 4L, etc). Just putting in a 4-pos switch will not guarantee all 4 settings for your vehicle.
Jejenkins, you hit it on the head...I can turn the switch "on" and I'm back to the factory mode. Just like fordfan said, I had the same issue with odd noises from the transfer case in A4wd under a load/acceleration. Do a search on "Front differential noise"...there are some good threads. With this new 2WD, i am free of all noise.
Good luck!