At idle I hear the idle get louder and then quieter. RPM's stay the same. There is a fluttering sound that starts and then the idle gets very quiet. Then the fluttering sound stops and the idle gets louder. Almost like something is turning on and off.

Also - I notice that after the truck warms up the whine from the turbo get a lot quieter. Is that normal? Is my turbo less lubricated when cold?
Truck runs fine just trying to figure out what's going on.. :confused:

03, you are hearing your fan ingage and disingage, vary normal.

Is the defroster on? If so, the ac compressor will kick on and off.