Which model do you have, early or later model? How much pinch do have at TDC?

The later ones are better than the earlier ones, and they are close to a Norvel .061 RC on a 6x3 prop. With a turbo plug head it will slightly out-power the Norvel .061 but can not match the .074. So there is nothing really wrong with these engines (at least on the later model).

The o-ring on the needle is not diesel compatible, you'll need to get a viton ring or something else than the stock material.

You could also try a Norvel .061 with an RJL head instead. Less weight, no o-ring on the needle, and Norvel seem to run well on diesel too.