I'm also wondering how much air you're putting in those bags, and whether you're adding before or after you've hooked up. My initial reaction is that you're putting too much pressure in the bags when empty and they are over pressurized when you hook up. Either that, or that toyhauler is waaaay heavy.
FWIW I put air bags on my 2001 Dodge dually because it rides like a lumber wagon when on the overloads. Too rough of a ride for my taste. But with 3,000 lbs. on the hitch, and 52 psi. in the bags, it rides very nicely.