Drop your gearing,mines a 151 and i droped to a 18/43,lots of getty up and go. I belive the 166 guys are going with a 19/42.It also helps to have a bit of happy juice when all eles fails.
Check your clutches, mark three chalk lines from center out on both ( X.Y.Z.) Pull some steep stuff. Look at the chalk lines to see were the belt is running on the clutches. What HP is your sled putting out? 19/45 works great for torque, but where do you ride and what elevation and weight ie: your sled yourself etc.? To many unknowns, more info bud. Most guys that run stock to semi mod are in the 1.85 to 2.05 ratio but it depends on lots of other perticulars.
Your best bet would be to contact some one like Highmark Rec, Slp, or Tri-city Polaris. They can hook you up with the right parts for your situation so you only mod it once. Believe me, I,ve done it both ways and taking the big hit once and changing the right parts will save you time and money.