Originally posted by Matt167

The difference is engines that are in plaines are designed to withstand the higher air pressure, I'd bet your mechanical injection adjusts in major ways to take the high pressure
Actually - as you go up the pressure decreases. in a normally aspirated engine, you simply lean the mixture as you go up to stop the engine from running too rich and fouling the plugs.

in my application, i am running turbos to normalize the manifold air pressure up to and including 25000 feet, over that i will have to lean the mixture to avoid running too rich as there will not be sufficient air.

but all ECU's that i have read about can handle that.