[TCallas]

I agree with the previous post, this appears to be an obvious brake booster failure or loss of vacuum to the brake booster assembly. I would remove the vacuum hose to the booster and check for a good vacuum supply. While the vacuum hose is removed, I would use a long plastic ty-strap and dip it into the booster to check for any water or brake fluid existing inside of the booster reservoir. I am curious if the vacuum check valve is OK? I do not have a schematic in front of me but that would be the next area to inspect. One last note, I have seen this before on a race car when someone installed the incorrect brake fluid reservoir cap. The cap was not a vent style and did not let the reservoir breathe. I am pretty sure that this is not your problem, just an FYI for all.