there is also a wire on the passanger side (green with a white stripe0 you can cut it and ground it out. that takes the reverse over ride away and you can go as fast backwards as you can foward. for the diff lock over ride just connect the 2 wire together.
i ride an 08 700 grizz and have no issues at all with over heating, keep the rad clean and should all be good to go. i know one other guy and he had to put a remote rad on. he tried everything too and that was the only thing that helped him.
i run shell fuel all the time,the company i work for has just shell cards. i have never had a problem with there fuel. i drive an 08 nissan titan and have 101,000km on it now and never had a problem yet. so i have nothing to complain about at the moment about there fuel. good luck