Thanks everyone I ordered the EHS lid and Uni air filter kit as this seems to be a major weak point of the Grizzly. Anything else I should consider is much appreciated. I also plan to block off the AIS.
Since you asked twice;
The low end pull can be greatly improved with C.V.T. mods that raise the pulley ration. This multiplies the engine torque (snap) produced just as using a lower gear in a truck is needed to pull heavy loads.
I got with COOP45 (Arnie) and ended up with him machining the movable primary sheave.
I use shim in combination with the machining to achieve the highest pulley ratio, without rubbing a hole in the C.V.T. cover, which produces best pull with the stock engine configuration.
The shim mod produces a linear effect which reduces the grizz top speed slightly so I cut the cam plate to counteract the shim after the grizz reaches @25 m.p.h., and this put the top speed back where it was. Arnie perfected the shim mod and does this work too.
Much of what I did was to match my grizz to the riding conditions in my area. For the best low speed crawling performance in the rocks using high gear, the machining and shim made the grizz user friendly with throttle control, then in more open areas between towns, once higher speed is reached the cam plate allows for higher speeds without stopping to shift gears.
To complete my combination, I installed heavier weight primary weights to regulate the up-shift for smooth cruising at lower engine r.p.m., and this increased the m.p.g.
Along the way I installed a heavier secondary spring to prevent belt slip from the high pulley ratio, and the heavier spring also produced more back-shift for improved engine deceleration. In the mountains, using less brake input is good.
Your area conditions may cause you to install some but not all of the above mentioned options.
The Yamaha C.V.T. system is very adjustable, I suggest you go slow and add mods one at a time to understand how each mod changes the overall system.