lowering the pressure of the gun does not happen with air, as it still runs off the same pressure whatever gas you use. I assume from your other threads this is a spyder we are talking about. You cannot drop the operating pressure by much, you may be able to get 100psi lower with al the possible upgrades, but by the time you've bought those, you could have afforded and impulse, which runs at 200psi stock, and is a better all round gun!
The point of lowering the pressure that your gun runs at is for three reasons, firstly it is much more gentle on tournament paint, which is very brittle. secondly it reduces the kick on the gun, enabling accurate rapid fire. thirdly it reduces your noise signature.
Hope it helps
by the way, air is a much better system than co2, and you can buy a 'preset' tank and screw it right into where your CO2 tank is now.