play with loosening one side and tightening the other more back and forth, I have also had some that I had to almost overtighten to finally get them to sit with the upper and lower gaps = instead of normal tightening they sat > and the angle would bind on the ridge of the throttle tube because the recess in the housing wasn't parallel to the flange on tube.

if the tube rotates in the housing off the bars tightened it is almost always either that or the od of the flange of the tube rubbing the id of the cutout, one or the other.