Can you tell me how I get the 317 at SL in COD with CEM? My procedure is:
All out (max rpm, max boost with boost cut out) then trim aircraft. Optimize rpm (slightly lower seems to improve speed), let it settle, retrim aircraft, then close radiator just as much to stay at water temperature still acceptable (120°C). Retrim if necessary.

I only get 300 mph at sea level. And this with several trials.