power brake booster

I think your booster is different than mine. But I'll check when I'm working on it tomorrow.

How mild is your cam? Do you know your vacuum at idle? If you're running power brakes and steering you want at least 10 inches of vacuum at idle. 12 or more is better. If you don't know your vacuum can you tell us what cam and we can try and find out. Pushing hard means you're into the "manual" part of the brakes. I occasionally have to do this when backing up or something, due to low vacuum. It could be a bad booster or not enough vacuum.