How loud and how much additional HP would I get from a MegamaxII in a 03 Foreman with a K&N jet kit??

 

I have the MegaMaxII and K&N filter on the Recon and Ranchers. The increase in power is very noticeable. Running more discs favors high end power, and running less favors low end. I run 6 discs as a happy medium, and it isn't terribly loud (the larger Foreman engine would no doubt be somewhat louder). There are two lengths available, so be sure you get the longer one if you are worried about sound. Be sure to get the K&N filter, because without it your air intake will become the limiting factor!