2G auto S/A daily

[CornFed2.4]

So trying to stall my car and seeing if I can build boost. It kinda works but can only build 6 before pushing threw the brakes.

Here's what happening.

When I hold the brakes down and give it gas the brake pedal pushes up like there's no vacuum.

I have a 1g intake and tom said there is a check valve on 1G brake boosters. Well mines a 2G and I don't see that on mine.

Wondering if anyone has had this issue and what to do to fix it.

I've read toucan pump the brakes while the car is off to relief vacuum pressure in the line.

Thanks