If you set the turnon point to low, then as you roll into the throttle and hit that boost level, typically will feel a slight surging.
This is not Wide Open Throttle. This is like when passing on the highway. If you set it too high, the the car will see detonation when you go to WOT due to time it takes for alky to hit the cylinder. The more aggressive your combination, heads, cam, boost, gears, etc.. the more pronounced the detonation.
Cars with stock heads and cam run mildly with a 12 PSI turnon work great running lower 20's for boost. You increase spool time, breathing, etc..this changes. As does the requirments for alky at those different levels. At 27 PSI those requirements are much higher than 15 PSI. Hope it makes some sense.
Some cars at 12 PSI ping like crazy..others can go 23 PSI on pump gas without alky.. just depends how air is getting packed into the motor, timing, etc...