I am resurrecting this question as I too would like to know how to modify.  Looks like this is % of  gate opening? for turbo at rpm and throttle angle?

  I have this modified on a tuned file and unmodified on a stock file.  Leaving it unmodified when tuning makes the turbo spool a little strange when driving.

Curios as to the logic that goes into adjusting this.  Looks like it should be set higher at equivalent points when running higher boost but not sure how to know how to set it.  Trial and error?

Thanks for whatever info someone can share.

Thanks, will be reading.