Just on a side note, Could LPG mixture be a cause? Running to Lean? Does not backfire or smell of un-burnt LPG, Power and response is all good when running on LPG, if you re-start after about 10 minutes of sitting it starts hard, but fires quicker the less time it cools. If you "Pump" it, The un-burnt LPG builds and you can start to smell it, and it will backfire. I am starting to risk blowing the muffler apart.

Thank you for the troubleshooting advice, I will do what you listed and post the results.

Thanks Again.