Start with the spraybar pointed straight down the intake and tune from there. If you are able to get a good high end and a good idle but a fat midrange, move it very slightly in either direction and retune. It doesn't take much to have a noticeable effect. And yes, these are high compression engines made to be sold in Europe and Asia where nitro more expensive. It will run well on no nitro or 5%. Some run fine on 10%, while some will never tune right due to the high end having to run so rich to retard the ignition timing.