brake booster check valve question

[BTF/PTM]

So I'm in the process of diagnosing weird brakes, first thing on the list tomorrow is to see if the reaction disk is in place. Anyway, today I did the basic thumb check on the vacuum lines between the engine and the booster. There's vacuum at the manifold, vacuum through the check valve and vacuum through each segment of tube. But...

When I opened the check valve, and also the final segment of tube which made sense, it made (makes) a distinct sort of sputtery groaning sound as air get sucked through it. Is this normal? I didn't connect a vacuum gauge (don't have one) so I don't know if the vacuum changes strength, but I still felt it on my thumb at all points. Is the check valve supposed to make that noise? Anyone have experience with this?

p.s. - I also tried flipping the check valve around and reconnecting it, just to see if it made a difference. It did, there was definitely a loss of vacuum when it was backward.

[Frankensteinz2]

there should be a noise, but i haven't taken it off, and depressed the pedal, but if you fear its bad, just get a new one at z motor sports real cheap, but what is the problem you having with your brakes, that is making you check

[BTF/PTM]

I have the "weak brakes - weak brakes - weak brakes -CRAPTHEWHEELSJUSTLOCKEDUP" pedal sequence despite a healthy brake system as far as components goes. I had the vacuum booster rebuilt at a local shop (which in retrospect I should have done myself becuz after looking at it I realize I'm more than capable of doing it), the 15/16" MC is new, front brake lines are new, pads/shoes are new and all four corners have been bled.

there should be a noise, but i haven't taken it off, and depressed the pedal, but if you fear its bad, just get a new one at z motor sports real cheap, but what is the problem you having with your brakes, that is making you check