I was looking on the Teamtekin.com forum and Randy had posted the following
Post subject: Re: Boost timing Post Posted: Fri Feb 27, 2009 12:37 am
Boost timing is additional timing that is applied to the motor after a certain amount of rpms.
So if you're motor is at 20 degrees and you had 10 boost you'd have 30 total.
So going on that it is RPM dependant not throttle position