We discussed this topic a couple of days ago at the local dealership...high speed vs low speed wobble. "Assuming" the frame, wheels, and other stuff is in order, too tight steering neck bearings can create a high speed wobble. They can actually get tighter with use, according to their most experienced mechanic. Not sure why, but that's what he's seen...bearing friction and grabbing maybe the cause. He also recommends using the leaky HD Special Grease for the pack as it continues to flow and lube (and drip out).
So do a fall away (via the old # swings, or newer left-right-center fall-off distance technique) to check the bearing tightness after lubing.
Low speed (~40-50 on decell) wobble is too loose bearings, an imbalance/tire cupping, or whatever. Loose bearings in my experience with a RG I used to own. Never had the high speed problem.
Just sharing an opinion here, I'm not a suspension expert.