When i went through my ordeal last year i just replaced all my lines with regular rubber vacuum hose, the bulk stuff from napa, and i ran the hoses in easy to access areas. i probably got all the hose and generic connectors for about $30 i would guess.

The deal with the vacuum system is to free up resistence and allow the truck to move easier and hence give you better MPGs. Because when the hubs are engaged and everything is turning up front, but your not in 4WD, your in a sense pushing the front to turn, putting more resistence on the truck. The vacuum system keeps the hubs disconnected. As long as there is vacuum everything is disconnected, but as soon as you get a leak somewhere (hoses, actuators, check valves) then the vacuum cannot hold and it allows the hubs to try to partially engage.

My truck ran for a minimum of 8 months with everything up front turning before i realized it, i never had the grinding noise, Because the one actuator failed so bad to the point where no vacuum at all could build in the system and the hubs just engaged.

I will tell you though, i did have to re-replace the ones actuator after about 6 months because it was sticking a bit and wouldnt let go completely. So even though you just replaced the actuators one could be bad i guess. There should be a 12 month warranty on the parts (Mine from my dealership did) so maybe you can rip them off and take them in and get brand new ones. Just a thought.