Cycled instrument air to LLCV and verified that needle was 100% open as indicated by CDS -> Temporarily valved-in magnahelic differential gauge and confirmed CP7's level, 38" = 92% full -> Noted indicated vapor "head" pressure for LN2 dewar was low, ~5 psi -> No indication of parallel paths for vapor exhaust -> Adjusted exhaust pressure regulator 1/2 turn CW.