[hypoxia]

Yes there is no air there since I disconnected the valve.  Check your valve for leaks, lots of swivel fittings in there with sideways pressure from the air tubing.

The rear air tank appears to be solely used by that control on the side of the engine.  It is electrically actuated and you can see the red metal tubing that is just above it angled up slightly which goes around to the other side of the engine towards the turbo but I haven't figured where it ends up. Yet.