I swapped my intake manifold last year to an Edelbrock Performer TBI and cleaned everything from the TBI unit to the power brake booster tube. Well, I took the booster tube out of the intake manifold and it has some black crud in it. Its not a ton, its not thick and it still functions fine. I was just wondering if there should be any kind of crud or build up in that part of my manifold and brake booster tube???