06 21V PP Problems

I have been having some trouble lately with my PP. I will set it then it will get up to speed, engage, then slow down, then accelerate up to speed again when I have a lot of weight (2400# in ballast and more than 3 people in the boat, 1 in the water) and am using the wakeplate at maximum setting. Isn't there a setting I can change that will make this go away? No problem with a small crew, but if I add anymore than 2 people in the boat, I have problems. Any suggestions or should I bring it in to the dealer? I have had to have my unit switched out twice already. This is supposedly the new version of PP that has the Moomba logo come up on the display when you turn it on (strange, being that is on a Supra!) and does not have a water temp gauge in the sending unit. Any help would be appreciated.