i have a sct x3 tuner and im not sure what to set my timing at for the various rpm ranges 0 to 2000 2000-4000 and 4000-8000. my tuner allows for -14 to 0 for the 0 to 2000 range and the question i have is does the - stand for BTDC? adn usaully i end up having to use 91 octane.