After reading your other post with the extensive dyno data tables,
I too wonder if you really had valve float,
or maybe were seeing the “dark side”
of where tuned port intake manifolds resonance does not help boost air charge pressure,
but instead reduces it.

The 130 degree dyno room temperature,
and 104 to 107 degree intake air
is unusual.

The speed of sound in air changes with temperature,
so air pulsation resonance does too.