I've been following real-life startup procedures for the Malibu (youtube is a great resource) and I've noticed the fuel selector in the off position shouls actually be like having it as "both". It should not cut off the engines as it does in FSX.
http://forum.avsim.net/topic/359694-max-rpm-and-other-things/#entry2226463
Having the fuel pump to 'off' should have a similar effect as having the fuel lines cut.
Is there anyone that knows how to mod this?