I typed this before, and didn't post it. Avid aircraft determined through testing that the 582 would remain running if the pulse fuel pump quit if you had 1/4" ram air tubes pointing forward from your wing tanks. On my Avid MK IV with a Jabiru engine, I have no impulse pump, just an electric facet fuel pump that is only used for take off and full throttle purposes. I do have the ram air tubes as well. A couple of times I have taken off and forgot to turn the electric fuel pump on. Never noticed any difference in how the engine ran, although the few times it happened, I noticed my mistake and turned the pump on, once when I was probably 100' high. All that being said, you should for sure do a fuel flow test at the carbs to determine how much flow you get with just gravity feed. If memory is correct, you should have at least 1 1/2 times maximum fuel burn. I never had a second fuel pump on my other 3 Avids or 1 Kitfox either. Maybe I was just fortunate. Interesting note, I did have the Jabiru supplied mechanical fuel pump over power the float valve, and that caused the engine to flood when pulled back to idle. That caused one of my dead stick landings. That was what caused me to go to the electric backup and gravity feed. Not exactly your question though I guess. JImChuk