Sky..that tensioner pully isn't really a 5.0 thing.Was just something I noticed on a few V6's not to forget my own even.For the longest time I thought it was the A/C compressor but then one day I was under the car while it was running checking a leak problem and noticed the whine was lounder down there.I used my right elbow and carefully pressed it tightly against the backside of the tensioner assembly.Then pressed my ear into the palm of my hand.The elbow acted like a pickup device and I could hear that annoying buzz fed right into my palm.I unbolted the pully and later after I put it back on,noticed I must've put it on the other way since it was clean looking by the center.Well,that noise ended.But it still makes other noises like the bearing seems to be wearing out.Having a very tad bit of side to side play is a good give away also.
Does the noise get louder when you turn the steering side to side while parked? If it does,then you know for sure it's the PS.Having that milky color....water got in the resevoir.Make sure your cap is on all the way.If it is,either the cap seal has gone bad or water could be getting in through the small airhole on top (Cleaned your motor lately?) To flush it out,just remove the top hose from the pump itself.Get a drain pan and drop the hose into the pan.Get a 2 - 3 foot length of rubber hose (Don't remember exactly what size.I believe the heater hose that would fit on the water pump .. 5/8" ?).Plug one end of the hose onto the top fitting of the pump that was disconnected and the other end into the drain pan.The typical way to do this is to spin the motor over remotely.In your case,you have coil over plugs so you'll have to disconnect them otherwise your motor will start.The spinning of the pully will run it all out.Better to crank a couple seconds,wait a few seconds,crank a few wait..etc.
Don't know if it'd be a good idea to actually run the motor.It may burn something up in the pump since it's constantly moving.
And make sure it isn't your alternator shaft bearing making that noise.Since it is right above the pump.Had to replace the alt. twice because the bearing got quite bad....and quite loud.Wasn't exactly a whine sound.More like a hollowed out grinding/ticking noise.