Phinam on a stock sled, 350's are good to -15*F thats wide open for miles on 87 octane, i've heard there good to about -20 but havent done it my self. If you ride in warmer weather, like +30*f then 340's will be fine.
Get a tempa-flow from dmperf on here(classified section), it will adjust fuel flow for the temp changes. Easy to use and install, well worth the $125, its been proven to work and last. It will be one of the best mods you can do to a f5, jet it once and forget it.
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