D7E Not running up.

I hit the decelerator on my d7e low horse to shift into reverse and when I released it, the engine wouldn't come out of about 1/4 throttle. I checked all the decelerato linkages and weights inside the govenor housing, all seem to be fine. I have good oil pressure so iremoved the govenor plate to exposethe safety plunger that keeps the throttle from movig forward until oil pressure builds to the turbo. I was able to work it freely and also I ran the rack passed it by punching it in and then started the engine. It ran great until I lowered the throttle enough to run it back past the plunge, then it wouldn't come forward again. My question is, since oil pressure makes the plunger suck in, and its not sucking in, how might a clean out the passage if it is clogged. Or do any of you have any other ideas of what it might could be. I believe that becasue the enigne runs fine, when i manually push the plunger in and run the rack passed it, I have eliminated it being a fuel pressure problem or oil pressure problem to the eninge, since my I am getting good oil pressure to the gauge. thanks for your time