So here's the issue my heater is hit or miss sometimes hot sometimes kinda hot. Running at highway speeds I lose vacuum. I.e. My blend door shuts. I have not replaced all my lines but I cannot hear a leak. Also I do have a reservoir ball. Just put it in. When I did that I noticed the vacuum was much weaker than on other lines. Is this normal. Or is it a bad pump. I'm confused.

 

There is no vacuum pump. The vacuum source is the intake manifold. I would inspect the line carefully from the intake manifold to the reservoir.