Bad toe settings can definitely make your car feel floating and twitchy. Make sure they tightened everything down after making adjustments.
Do you have any aftermarket suspension parts or is it stock? There are limits to what the stock parts can be adjusted to (no front camber, limited rear camber and toe).
Here is the basic alignment specs. The Nismo is the same except it runs a little more camber (which helps chew up tires unfortunately).
