Hi, I have a 2002 GMC 1/2 4x4 with the 4.8 gas engine and I want to plumb in an Auto Meter vacum gauge that I have. The only vacum line I see, other than the one for the brake booster, is a small plastic line that comes from under the top engine cover and comes out on the drivers side of the engine and goes into a thing(?). Does anyone know of a good place for me to plumb in the line for the vacum gauge? Thanks in advance for your help.