I've been getting a whirling or chirping noise for about the last 4 years. I thought it was an exhaust type of noise since it only does it long hard acceleration, normally when pulling a grade with a trailer.

Recently I replaced an injector and upgraded the stand pipes and dummy plugs while I was there so I've been monitoring the IPR and ICP. I noticed that when the chirping started the IPR % would jump from 63 to 70 but the ICP only fluctuated about 100-150. As soon as the chirping went away, (maybe 2 seconds) the IPR would drop back to 63.

Whats wierd is that I can massage the accelerator either direction an get the noise to go away if I want, or after a second or two it just goes away.
Any ideas or anybody seen this before?