Dyno changed lifted cylinder

Today I tested the changed Y-2 cylinder.
Have to say I'm pleased with the results, I have defeated the Y-1 cylinder witch was until now my best cylinder.
I gained with widening the exhaust port and Chamfering the ports a sollid 1HP

Here you have four runs nicely to each other
26,3 till 26,5HP

Her one off the average runs with 26,4HP

Her the difference between the lifted Y-2 cylinder and the Changed Y-2 cylinder

Here you see the steps
Orange run - stock base gasket Y-2 cylinder
Green run - lifted Y-2 cylinder (0,9mm higher)
Yellow run - lifted and changed Y-2 cylinder

The question remains.
What did what?
Widening the exhaust port with 0,8mm should normally gain power where already power is, but here it is revving higher.
Rounding the ports gives a better explanation, because you change the timing a bid.

Will investigate this further