The curve needs to be worked to counter act the delay.
Average is 1 degrees lose every 1,000 rpm past 1,000 rpm
So it starts at around 2,000 with 1 degree and by the time you get to 7,000 its 6 degrees.
Timing is based off of piston speed vs burn rate (chamber design) so taking a fast burn head such as a trick flow that wants 34 degrees at 7,000 rpm doesn't really want 34 at 4,000
We've seen 40 ft pound torque difference by applying a correct curve.