Problem with boost pressure

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03 MSP
I've just notice that my under full boost my boost meter is going crazy. I use U.C. When i run it at all the needle on my boost gauge is shooting from 8-12 psi very quickly. It didnt do that for the first month i had it in but it just did it. What could be the problem? Its also does it with the U.C. off at normal boost. its hitting 4-8. Ive heard so many different things that could be going wrong and i dont know who to believe how to fix it. HELP
 
My guess is that it's all in your boost guage. I wonder if hooking a vac pump onto the vaccum line of the guage would be able to confirm this.
 
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