Woody's video explained it pretty well. If you're accelerating, or plain driving, then the SC on, unless you're coasting to a stop, stopped, or at any time in park or nuetrel (I might be slightly off with that description).

This means if there was something wrong with the pulley and it was on all the time, like when driving normally, then its just doing what the normal pulley setup does anyways.

My temps used to always sit below the middle line on the temp guage. After I changed my s/c water pump, the temps always sat above the middle line instead, due to air in the system. I've tried my best to get bubbles out and can now get the temps to fluctuate between the below the line area and above the line area, but I can't see to get it back to just sitting below the middle line, no matter how much bleeding I do. This is why I haven't bought the code 3 pulley. I think i'm borderline too hot like the original poster.

Maybe having extra boost can mess up an already bad intake air temp sensor? The IAT is the deciding factor in the s/c shutting off. If a bad IAT is signaling intake temps too high then the s/c clutch will no longer engage. Its a $15 part, maybe order one from autohausaz.com