I've got a noice coming from my engine bay at around 2000 rpm and up. It sounds sort of like the pushrods may be rattling. Happens when accelerating or under a load. Any suggestions what this may be? I have 68,000 miles and change my oil every 3000 miles. I heard the injectors for the 4.2 are loud so this may it too....and thoughts about this or anyone have the same problem?

 

The injectors are loud, but mine are most noticeable around idle.

A rattling sound under load could be pinging, also known as pre-ignition or detonation. That's very hard on your engine. There are multiple causes, but it is usually caused by poor fuel quality, or perhaps a bad spark plug. If the truck is running hot (clogged radiator?), that could also contribute to pinging.