After considerable time searching and reading I can't find this specifically addressed. I'm changing turbos, fueling, and intake all at once and am debating moving to speed density over MAF based fueling on a 9 ecu. Which is better for large altitude or air density changes? I'm after a setup that works best from sea level (English racing) to where I live (5,000' in a valley) to where I drive/work many days (9,000'). This is Montana so temperature varies from 100f to -30f every year. Tuning to one altitude is straightforward, but having one tune that works well across such a large temperature density delta is not. Thank you in advance for insight.

 

IMO, the factory MAF is going to be better based on your goals. It will more accurately control fueling based on measured air flow, altitude, and temperature changes and those tables were developed by Mitsubishi. I would only consider SD for that application if you were using a good aftermarket ECU with Baro compensation and had it properly tuned, which would require tuning to take place at various altitudes. I'm actually in the process of converting away from "SD" and back to the factory MAF on my IX.