Bugtracker issues dealing with Spitfire FMs :
1. Incorrect boost settings (Rolls Royce Merlin engines):
http://www.il2bugtracker.com/issues/370
2. Incorrect mixture operation (Rolls Royce Merlin engines):
http://www.il2bugtracker.com/issues/102
3. Incorrect mixture position (Spitfire)
http://www.il2bugtracker.com/issues/18
Please do vote, it seems the devs are listening and are basing the fixes on the number of votes.