I'm the one who posted this topic some time back, and I can tell you for sure the problem is with the Brake Booster Pump! Affirmative.
Read my post in this thread:
Upgrade Master Cylinder?
I've replaced so many other parts (brake rotors and pads, idle control valve, ignition control module, plugs, cables, cap and rotor etc.) that I'd almost wanted to give up. But I was lucky at the end, albeit much poorer.
Go replace your booster pump, it must be leaking like mine was.