problems with PP Stargazer

I have a the PP Stargazer on my boat and I have been having troubles with it keeping speed. It will vary a 1.5mph either side of the set point. I have done all the suggestions from perfect pass so far and this is the best that I can get it to run. I am running 2k ballast in the boat if that matters. So my questions are how good does your stargazer hold mph and what are your settings at (kdw). And does anybody have any other suggestion to try.