Sorry, this is probably way too late for you, but may be of some use to someone still running one. We had the same problems with kangaroo fuel on long motorway journeys. Never any water in fuel. We came to the conclusion that it was dirty injectors, so have been using diesel fuel cleaners ever since, which sorted the problem as long as we only use cheap supermarket fuel. It doesn't like any of the branded fuels. The latest time we used Redex fuel cleaner which so far has lasted the longest. Current mileage around 218K.