[madmaxx]

It would seam if the previous brake set-up was working say from car 2500? and before why would they change? and since they did, the problem would have to attributed to what they changed. If they changed the master cylinder and calibers then it could be either or both. I have a hard time digesting the 427r vacuum, their have been hundreds installed in spf's and now it is an issue?

I am curious if this is an isolated incident or has every car after chassis # experience a problem?

Rather simple system in terms modern car systems with traction control, anti-lock etc. There is a brake booster, master cylinder, lines, and calibers. Even if you had low vacuum the car will stop you will just have to push the barke pedal harder, if you push the pedal to the floor and the car is not stopping regardless of the brake pedal effort than it is not an engine vacuum issue.