In the morning when I leave and when my engine is cold, every time I push the gas pedal I get a fairly loud growl from the engine compartment. It growls until the truck gets up to about 10 mph and then quits. Once I have gone a mile or so and the engine warms up a bit, the noise completely goes away. I don't think it's anything really serious, but I'm really curious as to what it is. Any ideas?

 

Growl, huh, got a tiger in your tank. Yuk yuk yuk

How about the EGR valve as possible source. Just an idea.