Ahhh, so your running a similar system to what I have.
Because your manifold is individual runners there needs to be a vacuum port tapped into more than one intake runner.
Have a look & see how many intake runners are feeding the vacuum hose that in turn supplies the brake booster.
I tried one on my setup, (has a moderate cam) & that was not enough vacuum.
Now I have the vacuum supplied from 4 intakes & it still really needs more.
Brakes are OK, but could be much better.
(Difficult & time consuming to tap into more intake runners with the intake installed on the engine).
Hence the need for the electric vacuum pump.
regards,
Tony.
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