highway noise

[halfadeuce]

So last Sunday I was driving back from the Pomona swapmeet and I noticed a type of groan noise from my suburban at highway speed. It's not a clunk or grinding noise. It sound familiar to tire noise but it goes away if I let off the throttle or if I'm above or below about 1800 rpm. I can't tell exactly where it's coming from. I was thinking either water pump or power steering but I'm not sure. Anybody know what it can be? Also I noticed that the hose from the pcv to the bottom of the carb was collapsing when I give it throttle. I replaced the pcv but am not sure if that can be related in any way.