Its possible that your weight distribution is light on the front end. Run your coach over the scales so as to weigh front and rear separately. My coach tracks perfectly and can be driven with one finger on the steering wheel while rolling down the highway at 70mph and I have made no modifications. I keep my tanks at very low levels and store heavy items as far forward as possible. Lighter items in the rear compartments. With the galley mid ship, tanks and closets and dressers aft and a substantial coach overhang aft of the rear axel and hitch weight from towed vehicles, I suspect weight distribution may be a problem with some coaches. Weighing the coach is cheap at truck stops. I run 90psi front and rear.