ok my polaris 300, i have went from a 155 to a 165 main jet, white primary spring, and free flowing muffler.. what should be next for me and my quad?

 

You could put a K&N air filter in it, or get rid of the stock air box and put a K&N clamp on filter on the carb. Because if your putting more fuel threw it then it needs more air, the old saying is "fuel and air makes horsepower". I hope this helps ya!