Frustration
- Brakes aren't as strong as I would think they should be and pre-pumping them doesn't help.

Symptoms
- Pumping brake pedal causes RPM to drop ~50-100rpm per pump.. pumping it fast about 5-10 times will cause the engine to stall*
- Pulling the vacuum hose going to the brake booster and putting my finger over the hose while someone pumps the pedal prevents from the RPMs from dropping.


Things I've Tried
- Replaced front calipers and pads
- Replaced rear shoes and hardware
- Turned all 4 rotors
- Bled brakes twice
- Replaced vacuum hose line going to brake booster.
- Replaced brake booster**

* This is not the surging idle issue. I've seen that before, it's different.
** No leakage detected from master cylinder when I replaced the brake booster.


I thought for sure it was the brake booster when I was able to get the RPMs to stop dropping when I plugged the vacuum line to the brake booster, but with a new brake booster and vacuum hose in, it's doing the same thing.

Any ideas on what else I should check?