rzr s not running

It all started riding around the neighborhood one nite as i pulled into my driveway a check engine light came on (636-2 cps). It quit immediately and i took it to dealership. They found the harness was laying on the coil and said that was my problem(it had a frame swap, reason for harness being routed wrong). I picked it up and took it to royal blue and rode all day no issues. The next weekend i took it to windrock and rode 30 minutes and same thing happened, ended up towong it back to trailer. Messed with it at home and got it to run again, so the next day i took off riding and within 30 minutes it backfired loud, check engine light came on and quit. For a little bit it would start up, miss, backfire and quit. Finally got it to run normal again and rode another hour and it done the same. It would only start and run for about 5 seconds missing and shut off. Took it to dealership that done frame job and they have had it all week with no luck. Any ideas? It has 1455 miles on it and has never had issues with running til now. Please help im dying to ride.

with it backfiring sounds like the fuel pump is going bad.

Ditto on what bush said. Check your fuel-pressure.

Dealership said today they also think it is the fuel pump. Looks like ill be trading before it is fixed tho unless i change my mind in the next 2 to 3 days. Thanks for the reply guys