Re: 3.0 diesel turbo
I can sometimes hear mine with radio off and it on the cooler side of temps outside. During the summer I could never hear it.
If the previous owner did some work to it, then you may hear a little. Work done would include removal of the bean shaped plastic thing sitting behind the radiator. This is supposed to help muffle the sound of the turbo. Some other have changed the plastic tube from the filter housing to the turbo. I dont know if a change to air filter would make any difference; I use the paper filters like AC Delco or Wix Filter will filter the best for the turbo.
Worse case is that you have an air leak somewhere in the intake piping AFTER the turbo. Some people have reported some minor holes in the intercooler.
2008 Ltd CRD QD2
GDE Eco, EHM, 2014 Rubis
Turbo Res Delete, 171,000+ miles