Since the problem is not equal in right and left turns, I've got a feeling the IFS crossmember has not been installed square with the frame or there's some other sort of difference in the steering, right to left. It sounds like one of the tires is turning at the wrong angle, and the front tires are fighting each other in turns.
THIS PROBLEM PROBABLY WON'T SHOW UP DURING A CONVENTIONAL WHEEL ALIGNMENT.
Good luck!
Jerry