mrennie wrote:The FEF-3 has a back pressure gauge that shows back pressure and (when the throttle is closed) vacuum in the cylinders - it's much more useful than a steam chest pressure gauge.
This thread states as much: http://www.trainorders.com/discussion/read.php?10,1637993,1638059#msg-1638059
From the thread I conclude that the Valve Pilot recordings could be used to reward a crew for running their loco efficiently.