Here's the scoop. I bought a new 2001 Banshee and installed the Motion Pro twist throttle kit. I then noticed that the throttle seemed to stick a little and that during wide open runs in the dunes it would lean out a little(just on top end). This bothered me so I tried the next logical solution. I pulled my needles up a 1/2 notch. It only caused my quad to load up at mid throttle. This was very disconcerning. I tried cleaning the carbs, changing jets and needles, honing the slides and jet ways, etc.. Nothing worked. So my friend (Banshee owner) and I looked into this and this is what we found. On a stock Banshee with stock carbs and caps, you will notice in the windows on the sides of the carbs, that when you hold the throttle wide open, the white dots on the slides center themselves in the windows. This is a good thing. Now look at the dots on the modified carbs at full throttle. They should enter the windows at the same time but you'll notice that the slides overextend. See the aftermarket caps allow the slides to pass maximum throttle. This is the problem. See after a certain point on your throttle no more fuel is being introduced but more air is, thus causing the lean condition at top end. See once the needle passes the top of the jet no more fuel will be introduced, but with the aftermarket caps it still allows your slide to open farther, thus allowing more air. Also we found that when the slides came up to a certain point that the air and fuel pressure would be great enough to hold the slides open. So this is how we fixed this issue. My friend took some measurements and came up with a spacer that installs in the aftermarket caps. He allowed about .002 over overextension but not enough too lean the mixture out. Not only did this fix the lean condition but it also fixed the sticky throttle condition. If anybody is interested we have the dimensions or program to run these on a CNC machine. We have also contacted Motion Pro and other manufacturers about this issue. Hopefully this helps.