so the other day I noticed I had no power brakes after racing past this moron on the road the other day after passing him I needed to make the next turn hit the brakes and had no power assist until rpms dropped to 4500 or less. I then decided to smoke test the brake booster and it and it was leaking so I replaced it with another one, used but it was working good on the truck it came off. still I have a rock hard pedal at high rpms. trying to figure out if im supposed to be using the 3.4 booster or not.
Your brakes work off of vacuum. The engine vacuum is greater at lower rpm or when your not pressing the gas. When you push the pedal to the floor the engine doesn't create enough vacuum for power brakes.