'05 Silverado - High Pressure Air Condition?

I have what appears to be a high pressure sound coming from the air conditioner on my 5.3 V8. It gets quite loud (others at traffic lights look at me strangely) at idle. I've heard that there is a mod on the orifice and other parts required to fix this. You can hear the pressure dissipate even after turning the engine off (again, quite loudly).

Anyone have similar problems?