I'm not all that familiar with this topic of disconnecting things Steve, maybe SteveB will have an idea. My take on it is that some crud in the booster hose, after alot of miles,is normal. I believe it gets in there from slight oil seepage from the vacuum pump. I don't know how it gets in the booster line with the pump producing vacuum, but I've heard it does somehow. I'm not sure what the white junction is you mean. What I am recommending is the whole thick line from the steel line that screws down on the vacuum pump, back to the power brake booster. I believe this will solve your problem for many many miles.