1995 u42t 3g83 Anyone know where ported vs manifold vacuum takes place on this rig? After the throttle plate looking from the air filter side i have vacuum lines on the left that deliver vacuum at idle. Then there is a white little cap, then a couple more vacuum lines to the right, towards the front of the vehicle, that, i thought were ported vacuum but do not seem to deliver any vacuum now. Ive been chasing a poor running condition that i believe to be this lack of vacuum to the advance on the distributor. I have installed a T in the good vacuum source and put to the distributor and seems to run good now. But i have no 4wd. I assume it is controlled by this non working vacuum source but not sure where. Any ideas on what could cause this vacuum blockage? I did recently install a cold air intake but made sure all vacuum was where they came from in the path and the truck did work fine for a couple weeks like that
