Brake booster going or vacuum pump?

[Junkycosmos]

Looking for ideas here please.

Brake assistance at idle is week on 2 or 3rd push of the pedal while at engine idle.

For example when parallel parking or driving in slow traffic you have to stomp really hard on the pedal after idling a few feet and then using brakes 2 or 3rd push.

Zero sponginess in the pedal, it's a rock, and when you step really hard the brakes work great.

Any engine speed above idle and the pedal feels normal.

Only other thing I can think to mention is hearing a faint sound from the engine bay while holding foot on brakes. Almost sounds like running water does in the house pipes from a few rooms away. Not a loud sound, may not be new, and I may be noticing it now since while troubleshooting.

I ordered Ordered vacuum pump seal kit from BMP Design to try but I'm not sure if this will fix.

http://www.bmpdesign.com/search_resu...h_query=305162


Thanks
Junkycosmos

2905 4.8is @ 92k miles