While I applaud the Bilsteins {I have the heavy duty models my 24' Nexus Class C and they are awesome}, and since you already have the air bags {which should have been totally unnecessary }, there should be nothing further needed except getting the rig weighed and your tires properly inflated for the load they are actually carrying.
After market crapola to make a Class C ride/handle/drive decently is all a huge scam. If it did not perform well on the thorough test drive {you did do a thorough test drive, right?}, why did you buy it? A trip to the Cat Scale and worst case perhaps having the alignment re done should solve all of the OP's problems. If not he bought the wrong coach .
Any new Class C should roll of of the showroom floor with zero handling/ride/performance issues. Salesmen don't like to have you take a serious test drive but if they balk... Run Forrest run" to a dealer who will allow you to thoroughly test the rig.
As always... Opinions and YMMV.
:C