Mods r.. dyno port twin inframe exhaust, ported cases & jugs, 40 over bore, +4 timing, procom cdi, boyson 2 stage reeds, boost bodle lol.. I can't remember what my elevation is ill have 2 look.. and I think I'm running 210s in it now could b wrong snowmobile season brain washed me on my quads lol.. I was just thinkin there was a rule of thumb on them like jet up 5 n work from there of something