High Speed Auto

I’ve been trying to get my little racer copter to do auto missions as quickly as possible… But am failing.
To start, lets talk about “speed up”.
In stab or acro, the copter goes up extremely fast! Much faster than I’m comfortable with :).

But, in auto, I can’t get it to go faster than about 6 meters per second.
I set the parameter to 10 and even 20 meters per second, but it never goes above about 6.
I know it is going much much faster than that in the manual modes.

What else could be slowing down auto modes, other than the simple speed settings?
I can imagine for horizontal travel there could be lean angles and other limitations… But what about just going up?

Thanks for any help.