I've got the 4.6L in my truck with just under 70,000km. I replaced the serpentine belt about 5000km ago. When it's cold and the engine is idling, there's a pully or some spinning component on the front of the engine making a bunch of noise, like a bad bearing or pully or something, and it does change with a blip of RPMs. It's annoying and getting progressively louder, any ideas on what it may be? Are some of the pullys more likely to wear out first than others?