brake booster check valve

[Todd King]

  <<<
  >There is a check valve in the brake booster to prevent pressure from entering 
  the booster on many cars.  Under boost >you loose all effects of   >>>
  
  On the plus side these valves are just inexpensive plastic valves available 
  anywhere; they go inline with the hose to the booster (at least on GM- don't 
  know about other) so really ought to be easy to have one... 
  
  Todd_King at ccm.co.intel.com