Unbolt the fuel tank and slide it back. Check the wiring harness under the tank and check and make sure none of the connections to the four coils mounted in front of the tank are bad. I unbolt all mine and move the wires from under them and electrical tape them to the top of each coil. It seems to keep the wires from rubbing on the tunnel. You can unplug one wire at a time from the plugs to help you find the bad coil. If it's popping and cutting out I'm guessing one whole side is bad and you have a wire harness issue and not an individual coil bad. The sled doesn't need both coils working on each cylinder to run, I piled my sled up last year and broke the top of the spark plug off into one of the caps and the sled ran fine back to the truck on 3 plugs.
