I am looking for a source for an air filter (Fleetguard AF1838M or Donaldson P14-8043) for our coach. I called Cummins and they told me that they are not stocked anywhere and would take 2 to 3 weeks to order! Aside from that, They wanted $102 for them. So what did they tell a customer who's in for service " You need an air filter but your coach will be here for two...