If your car is not driving straight after adjusting the servo check to two things listed below:
1. Take the front wheels off and look for hair or fuzz around each axel. This has happede to me before.
2. Make sure each wheel spins freely after tightening down the lug nut. If one of the wheels is tighter than the other, it will veer to the side, which ever is tighter. I spin each wheel with my finger to see if both wheels spin for approimently the same time. My front and rear wheels are pretty wobly but my car still drives straight.
Also, check the rear wheel for fuzz and over thightened lugs.