Yep I cut one open and there's not much going on in the inside... As you can see from the pictures it's basically open until there is enough vacuum on the intake side to pull the diaphram closed then while that vacuum is present then once you build up enough POSITIVE pressure in the crankcase it will force open the valve again to relieve the pressure in the crankcase. The spring holds the valve OPEN during most of it's life - it should only close when the truck is in off idle conditon but judging from the spring pressure of mine (once I cut it open) it should only close during higher RPMS.
On edit - as you can tell mine was SHOT to say the least. I was very very carefull on cutting mine open (basically pryed it open for the most part) and the diaphram is VERY VERY THIN so cleaning is more than likely not much of a successful venture... I say just just toss it and run a RDT but as you mentioned you use your truck in business so that's not an option... so it's off to the Ford Stealer for you...