Need Help Install vacuum gauge

2009 Toyota Tacoma 6 cylinder,
I added a vacuum gauge, and I think I have it hooked up to the wrong vacuum line, I have it taped into the vacuum line right behind the air intake that goes into a black cylinder, the gauge works but does not fluctuate. I had one hooked to up my 1970 Z-28 and the needle rocks back and forth when you hit the gas, it was tapped directly into the intake manifold.

Is there another line that I can tap into or do I have to tap directly into the manifold? The gauge looks cool when it rocks back and forth.

Thanks for the help

 

If you are looking to get a true intake vacuum, the best place would be to connect straight to the intake manifold on the engine side of the throttle body.