never really noticed before, but lately every time I look, the needle on the guage is always about a 1/4 the way too boost. Is the needle supposed to rest on the black line for vac or does it always sit higher. I never took notice to detail on that but i've been trying to track down a whistling noise for over a month which is possibly a vaccum leak and this came to mind. Any help is much appreciated....

 

The guage is mostly used when the supercharger kicks in. If you notice the zero, the zero means that the supercharger has kicked in but is only sucking in the smae amount as if the supercharger was not kickin in. Below the zero means the supercharger is not working, it is just sucking in air on it's own (the motor). Above the zero means that the supercharger is working and it is sucking in Blah pounds in of air. Now if the needle rested on the bottom that means there is NO air being brought into the engine.