I've not done any of the suggested fixes yet. To be honest, the thought of drilling a zillion holes, wrapping everything in shielding, etc on a $50.000 truck, gives me the willies.
One thing I did notice is that if I am tooling down the highway at 70 MPH, and take my foot off the gas, the noise decreases to S0. Giving the truck gas, spikes the noise to S7. The more gas I give it, the more noise.