Part of that "lack of directional stability" or "lightness" could be there not being enough caster. A VW barely has enough caster for 65-70 mph, and dropping the car even just a couple inches can make it hard to control even at 60 mph. To make the car safer at higher speeds your car may need a pair (or even maybe 2 pairs, depending on how low the car is and how it was lowered) of shims underneath the bottom beam of the front suspension.
http://www.geneberg.com/advanc...ster&x=3&y=7
As you can see, they're not expensive; buy 2 pairs (and the longer bolts) and if you don't use the 2nd set you can always sell them. Al