Constantly correcting steering

I took it for a front end alignment to a well known in this area Truck shop and then brought it elsewhere to have the SafeT Plus put on. Wind is BAD, trucks going by not so bad, driving with no wind on highway it is a constant back and forth on steering wheel to go straight, if I straighten the wheels and steering wheel is slightly to the right(not centered) it pulls to the left a bit. Two different shops have tried to get it to just go straight with wheels going straight and it just does not adjust right. The steering wheel is still a little to the right. I do not think they tried to put the steering wheel on straight because they spent so much time trying to get the Steering Plus to hold the wheel straight without constant pulling one way or the other. I am not liking it but have drivien about 500 miles and made it in one piece but passing a long truck is very nerve wracking since I am constantly moving the steering wheel. I had a Winne Adventurer some years ago and NEVER had this problem, it was solid as a rock.