The latest version is D2 but it brings no real benefit to you as it only has different electronic components. I do not recommend an upgrade if it is working properly.

If you wish to have the most recent version of FADEC ECU which includes the DATA terminal and a good number of customer adjustable parameters such as start fuel ramp, de-rating of max rpm, start mode options, glow driver power etc. etc. the cost is approx. $450.00

As I said previously, I would suggest staying with what you have unless it has developed some sort of operational issue.

Best Regards,