I think we're both right and describing different things. The air in the engine will be 4x as dense, but the flow rate will be the same. The air in the tank c

I think we're both right and describing different things. The air in the engine will be 4x as dense, but the flow rate will be the same. The air in the tank cannot change density, and will therefore have a 4x higher flow rate. The result is that storage is worth less strokes/breaths at depth.