Kinda sounds like somethings rubbing, only happens when my foots in it pretty good, doesn't happen in park / N only when in gear.

Any thoughts before I ask my brother to lay under the truck and listen around while i brake torque it? probably not the safest thing hahahah.

Plenums fixed before u ask.

 

Check the heat shield on the side of the gas tank toward the driveshaft. Mine had broken loose, and under load, the driveshaft would rub on it. Made some horrible noises......

 

While your brothers is down there have him check your
U- joints too.

 

Check the pinion splash shield near your rear diff. its a metal ring around a drive shaft component that protects the pinion seal. Can't remember which component it is attached to but it seems to like to rust off then free spin. It usually sounds like your dragging a chain when you get on it.

 

I second HeyYou. I had the same type of noise (sounds like tinging sheet metal TING TING TING TING TING?) really fast? heat shield was rubbing the driveshaft knuckle a little bit. It sounded like something horrible was about to break at any second.. I just ended up bending it back towards the gas tank and its been quiet now for 3 months!

 

I had the heat shield on the cat converter come loose and rattle. I went and wrapped a carb spring around it and problem solved.