Yes it has been entirely too long.... started within the first 100 miles.It all depends on what BRP is going to do ! A tune can desensitize the misfire fault but you don't want to do anything that may jeopardize your chances of warranty. You may consider reaching out to a vender like EVO or PWRTune to see if they have any suggestions or can put it on their dyno and fix the problem. It is obvious a typical dealership doesn't have the capability to figure this out but a tuner that can get in the ECU software and watch what is taking place probably can. It may cost you a road trip but this has went on entirely too long , you need to ride that thing.