Not sure on the EVAP problem but you might want to check here for into on the possible noise issue:
ECGS clamshell bushing headcount?
I just did the bushing kit and it wasn't too bad. Maybe buy the parts and see if you can get a local shop to do the work. Better yet, track down some buddies in the local 4x4 club and tear into it. I'd bet it will be way less than the $400 and should last forever.
There's a TSB for the needle bearing and step 1 of the troubleshooting is that it makes noise in 2wd but not 4wd. It sounds like the full time 4wd (V8) models don't really have this issue. However, I wonder if the bearing still goes bad but since the front is always pulling you don't get the noise/vibration.