What does the low pressure chamber due in a Spyder paintball gun?

I have a Spyder Compact 2000 paintball gun that has a low pressure chamber on it. I was wondering what it did for the paintball gun. If I wanted to add an expansion chamber, would it due the same thing as the low pressure chamber, or would I want to keep both?

All help would be greatly appreciated.

TIPPMANN A5 PAINTBALL Marker Gun M4 RIS SNIPER SET

TIPPMANN A5 PAINTBALL Marker Gun M4 RIS SNIPER SET

Tippmann A5 Marker, A5 Cyclone Ammo Hopper, 16″ M4 Ported Sniper Paintball Barrel, Tippmann A5 Tactical Stock 6 position Adjustable, Fixed Sight Rail/Carry Handle, Tippmann Tactical M4 Mag Expansion Chamber, GXG Stealth Mask with Visor & Anti Fog Lens or PMI Xrauk with visor and anti fog lens, 20oz CO2 Tank with Pin Valve, UFD Heavy Duty Coiled Remote with Quick Disconnect On/Off, 21″ GXG padded gun case, Tippmann Double Trigger, Deluxe 4+1 Harness, 4 – 140 Round Tubes, 2oz Prem (more…)