Well I spent yesterday working on the truck and hopefully all will be well. Replaced both actuators and reconnected the vacuum line. The right actuator was so bad I couldn't even compress it by hand when it was removed. It felt like something was inside the unit blocking one side so it couldn't retract. Lots of tacky black (used to be) grease to clean out of there. Left side looked less bad, but both sides showed evidence of water contamination. The truck spent the 1st 3 years of it's life in Michigan, and it shows on all the unprotected metal parts underneath. All the vacuum lines are very good-no leaks at all. When I take another longish drive I'll see if that fixed it. Only things left would be the solenoid, the check valve nearest the solenoid, or the vacuum box. At least the hardest parts are done!
While I was at it I replaced the brake pads on all four wheels and flushed the lines/new fluid, and replaced the fuel filter. By the local dealer's estimates, all told I just save about $1200 in labor.