Ditty, great job, thanks for the discriptions... but need one thing cleared up... our trucks do or don't have a blow off valve? You stated that we don't have throttle plates, but in your discription, it seems the throttle plate is needed for there to be a blow off valve, and that, my friend, is where I get lost... the sound we are all hearing, the 'whoosh', the un-needed, compressed air, as it is released. It would make sence to me that there IS a blow off valve, when used, releases the air, and "whoosh", we hear it... and the throttle plates are only in gas motors.
Sorry if I"m splitin' hairs, but... as I said earlier, still learnin'... thanks again for your knowlage in this area...