Need help, spitfire with very low rpm on full throttle

[NedLynch]

Complex Engine Management, option in the realism panel.

I recommend you read up on it, use the search function to get more info, it's really great once you learned how to fly with it turned on, including overheating of your engine. Try it, learn it, once you get the hang of it you'll never want to go back flying without it.