Dear Peter,
Answer to your question "Is the gravitomagnetic system different or not from the electromagnetic system? Are they the same physical system?"
Based on what I know about gravitomagnetic systems (a strictly passive knowledge because I made no contribution to this subject), I would say that the two systems share some strong formal similarities, but that they are not the same system. But please ask an expert, not me. Better yet, do what all other physicists do: Study the original papers and you won't have to ask anyone.
Good luck with your octonionic model of gravity.
Regards, Emile.
