Headsup for Brake Proportioning valve booster problems

[71chevc10]

Just an FYI
My brakes didnt function well my rear brakes not activating and hard brake pedal.
I chased my tail on my brake system replacing booster, master cylinder wheel cylinders proportioning valve. I checked vacuum at the carb which was 18 which is spec for the booster.
after doing all this and no change in braking I looked at the vacuum t on the manifold and the inlet was undersized I replaced it with the correct size inlet and my brakes are great.
I hope this helps someone else if they are trying to find the problem that I had