THE ORIGINATORS OF THE FUEL MOD---Hot Rod Sled Shop Inc. bring you the Fuel Mod for the 2017-2020 Ski-doo Rev GEN4 850 ETEC. We devised a way to fool the factory ecu into "thinking" its colder out so it adds fuel and the "HRSS ORIGINAL FUEL MODS" were made for the 800 etec in 2014 and now we have them for the 850 ETEC and have been promptly copied by one of our vendors "$IKEMAN"-WE APPRECIATE THAT. We have spent lots of dyno time combined with field testing for 3 seasons now with our fuel mods to give the precise amount of fuel matching your motor mods. This works really well with piped sleds, ported motors, big bores and mod 850's. Our dyno testing shows stock 850 etecs need no extra fuel but our ported motors and several of the big bores use this mod to add some fuel with no check engine lights or check engine codes like some of the fuel programmers out there. This is a true plug-n-play (no splicing, cutting etc.) Our fuel mods are being used by several shops for modified trail motors and big bores. We have stages 1-3 so call for your specific needs and yes we hear its been copied -----CALL THE GUYS WHO MADE THE ORIGINAL AND HAVE SPENT THE MOST TIME DEVELOPING THE PRODUCT!