+1 on all the shim stuff above. Just be careful not to take the 1 x thin .1mm copper shim out too soon. Make sure you have fully broken in the motor and it can be turned over by hand in the buggy when hot before you pull the .1mm shim out, especially if you are going to be running 30%. Best to also run a medium plug or cooler (say OD 97T or LRP #6) if your going up to 30% with this shim removed. Depends on your ambient temps of course.
Enjoy your racing. Glad to hear the GO GX's are doing the business.