I just rebuilt my carbs on a 96 GTX. It was running fine before the rebuild with the exception of some surging at full throttle. After rebuilding the carbs, the ski would start up, run for a few seconds and then die off the final sound was an incredibly loud backfire. Then I found that it blew a hole the size of a tennis ball in the exhaust tube. I spent lots of time going through the forums and internet posts looking for the possible culprit. I removed, disassembled and reassembled the carbs 3 times, replaced the gray fuel lines, cleaned the fuel valve, verified the pop off, changed the plugs and wires, replaced the gaskets on the intake and carbs, replaced the o-ring on the rotating valve plate. You name it, I did it. The solution after 20 or more backfiring episodes...restricted fuel filter. It was allowing fuel through, just not enough. I feel like a knucklehead for not seeing it before spending two full days working on my ski. Thought I might pass the info on so someone else doesn't wast their time like I did.