I know this post is somewhat old and you might not need this information anymore, but I had a similar problem and someone here on the forums told me to put diametric creme on the connection below the driver's side rear door that powers the fuel pump. I have not had the problem since. It seems that the connection is vulnerable to getting wet and can cause the fuel pump to randomly lose power. I hope this helps. If you need more specifics about where the connection is let me know.
Moses