Air Fittings

Milton V-style fittings are the highest-flowing normal-sized air fittings available. I went from M-style to V and noticed a significant improvement. I've had two shops convert from M- and A-style based on using mine, as have a couple of my friends. If memory serves, they even outflow the massive P-style, etc. As a bonus, you can still use your tools equipped with the older M-/A-/T-style plugs until you get around to upgrading those.
They're available as the "purple" fittings you see mentioned above, but I'd avoid those for durability reasons. They're also available in steel and brass with the same performance but much longer life.