My plane is a high wing, gravity fed to a collector tank then down though a very short, fat hose (with a course filter in line) to the pumps box which is at a lower level still - flat on the floor under the seats which also means they are in perhaps the coolest part of the plane. Rotax require the pumps to be low down, and having them gravity fed, ALL the way, should help them. I guess they don't deal well with low pressure on the suction side. And of course, an injected engine requires continuous fuel pressure so even the briefest interruption will cause a 'stumble'. Re-plumbing could be a pain, but going to Rotax-standard could be the answer. See the Rotax Builder Series for the collector tank experiments. The tank was higher than the pumps.
