Isn't that why the 4000's have the vacuum pump running of the cam for the power brake assist? On Wed, Jan 27, 2010 at 3:38 PM, Joshua Van Tol <josh at spiny.com> wrote: > Also, there's vacuum depletion to consider. The first engagement of the > brakes will have full assist, but each subsequent one will have less. That's > why our turbo Audis have hydraulic assist. >