STILL losing my cool with this AC Problem

Ok guys, thanks for all of your help so far. Here's where I stand so far:

Suggestion was that there was "AIR" trapped in the A/C system. So I had a full VAC. Evacuate and Recharge....and.....

Lookie at that when its 115 outside I have 45-50 air...!!! I was loving life:

FOR LESS THEN 20 HOURS...UGH

I was stopped at a light, A/C working fine, start off from the light and started hearing this horrible noise, almost like a 15 year old import with an exhaust leak.

Pulled in for gas...other side of intersection, stopped at the pump and put it in Park. Revved it a little 1600-2000 RPM's, and theres the horrible sound again, but now that I am really listning..it almost sounds like the fan is hitting the shroud..."CLICK CLICK CLICK" But fast and loud.

checked the clearance between the shroud and fan seem fine.

Have my friend rev it while I am looking at it....with the hood up irt almost sounds like a belt is slipping but with a mechanical sound with it.

Look at the AC compressor fearing that maybe it was "Siezing" and noticed that the AC belt Tensioner, as soon as the noise started was "flapping" up and down. So I thought maybe the spring in it was going bad, letting tension come of the belt and allowing it to slip.

Call the Chevy dealer, ask the guy if he's been replacing these lately and sure enough they have ordered 7 from the Hummer dealership in the past week(Same Part). Call up Hummer, told the guy that the Chevy dealer told me to call and he said "oh, you need a Belt Tensioner" without me even tealing him what part I needed. Made even more logic that was what was wrong.

Picked up the part...installed last night, Filling pretty confident we have got this problem licked...

Start the truck....REV the gas......SAME NOISE!! OMG...

So on to solve the mystery...any suggestions? Clutch, or just change the whole thing?

Clutch $175
Compressor List price $636 Wholesale for me...$380ish

My theory has always been when it could be two or more problems is to always repair the cheaper of the two and go from there..Works out 70% or the time...HELP me please

i would listem closly to see if u can pinpoint it but i would say the compressor is bad.

common problem with newer ck trucks is this noise. yes it is the compressor. GM PI01139c

What is GM PI01139c?