Here is the video of the sound

It happens during idle and while driving at the same RPM range. Pretty sure it's louder when when the engine is fully warmed up

Motor is built:
Mid Wet Darton Sleeves
CP 10:1 Pistons
BC H Beam Rod
Brian Crower Stage 2 Cams
Supertech Valves
Ferrea Dual Valve Springs

 

Here is a better video of the noise. It's only present at 2k RPM and mostly when the engine is warm. No noise above or below 2k...

 

That's resonance no big deal. Check the trunk, the torsion bar that raises the trunk resonates with the exhaust some times.

 

I was pretty sure it sounded IN the engine but the again...weird it only happens at 2k

not 1.9 or 2.1k only 2 lol

 

Thanks to inline pro the problem found

Wastegate dumptube was touching the subframe

all fixed now!