Originally Posted by gearhead1011
Sounds like bump steer to me. If this "freshly built vega" included any mods to the front steering/suspension bump steer is the likely culprit. If the front end geometry isn't correct the toe will change as the ride height of the car changes. When this happens it will steer the car in different directions as the ride height changes.
I would have to agree with gearhead. I think its going to be bump steer. I don't know why but I've seen more Vegas have this problem than any other. It may be because of the placement of the rack n pinion. I had one we fixed that when you jacked it up you would have 3/4" on tow out. The car also had 1/2 tow in if two healthy men sat on each fender. The tie rods where at too much of an angle. We used dirt track tie rod adapter stud. You got to start somewhere. Let us know what you find.