G'day and welcome!
I'm no expert so ill leave the diagnosis alone, however I can point you to the OBDII port! There are a few posts here regarding rough running issues and LPG dramas. Have you tried the search function? If you scroll down a few topics (and maybe onto the next page) I'm sure you will find something of help.
It is up under the dash in the LH (passenger) footwell.
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