Sometimes just going around tapping different things with a rubber mallet can help locate noises like that.
Maybe it's just something that resonates at a certain frequency in the rev range when the engine is putting out just the right amount of torque.
A couple weeks ago we had a Dodge truck come in with, what sounded like, something broken in the suspension. We started prying around on the suspension parts and couldn't find anything wrong.
If you hit the frame rail on the driver side with a rubber mallet hard enough, you could hear it. It ended up being a broken spot weld on the bottom of the bed where it mounts to the frame.

 

Nice find! That's the kind of thing that would keep me up at night!

 

I know what you mean. That was a strange one!

 

To close this out.

Motor Mounts were trashed. Replaced the mounts today and alls good in the hood.

Under heavy acceleration the motor would uncontrollably twist causing the driver's side cat to vibrate against the chassis rail and the passenger side cat to flirt with the front propshaft.

I can do holeshots again

 

Awesome! It's always nice to see people come back and write about the fix.