I too installed a Gravityworx throttle cable (6"+ cable for my XLT).
I typically back the idle screws out until the slides bottom out in the carbs with the cables attached, and then adjust the throttle cable adjuster at the top of each carb until all the slides open at exactly the same time when you hit the throttle. Takes a little time to do. You can also get a Uni-Syn carb sync tool, but I didn't have much luck with one on my sled for some reason.
Once that's all set, I then go back and set the oil injection pump so that at idle, the marks line up, or just a hair open (lever pulled just past the marks). A small mirror and flashlight make that operation easier.
If your idle adjustments were set properly before and you get the slides back in the same carbs they came out of, you can forgo backing the idle screws out, and just adjust the cables with the slides against the idle screws. Once you have the carbs even, use the single cable adjuster in the middle of the cable to set the amount of slack you have in the throttle. I have probably 1/8" gap between the throttle lever and the throttle housing right at the cable when I take up the slack. You don't want the cable tight because if anything hangs up slightly, you'll hang the throttle open and that's no good.
Oh...and make darn sure the cable ends are seated in the throttle slides properly and that you put the little plate back in over the cables that keep the ends from popping out of place.
Update: After checking the service manual, it says the throttle lever clearance should be .25 - .75mm, much tighter than the 1/8" I mentioned. I still think a little more slack is good, but ymmv.
