Fuel filters, air filter, valve adjustment, check for boost leaks, and check the e-brake for dragging. A friend just replaced the seized cables on a customer truck that was experiencing bad mileage. New cables, better mileage.

Funny you should say that RA. Few weeks ago I pressed my e brake all the way down to see if it worked and I think it snapped because I heard a pop then I release and depressed it again and I needed no effort to push it down. Could be that. I cleaned my airfilter and now I think I'm just going to buy a filter not a water separator. Unless I should get both. I live down a dirt road so I should've guessed I had to replace them.

Knowing that, I'd bet you e-brakes clamped on, cable snapped, and because the cables are seized, they have stayed clamped a bit. I'd do both filters. For the cost, it's cheap insurance.