Does the port get noisy when it gets into that dip?
I’m not surprised the port flowed better with the valve in it. The valve has some influence on the flow curve even at very high lifts.
I’ll dig out the Don Terrell book out and take a picture of a top cut valve and what he says it does.
FWIW my testing did not match his testing on the top cut intake valve.
But that doesn’t mean that’s always the case.
I’ve had to eat the big poop sandwich more than once when I was 100% sure that something always worked (or never worked) and then I found a case where stuff like a top cut valve works.
Thats where great testing and note taking like you are doing will pay off big time at some point.
I still kick myself for selling my flow bench but what’s worse is I didn’t keep all my flow tests and notes when I sold it. I should have at least made and kept copies of them.
That was really, really STUPID on my part.