I think the current EU standard for the average passenger is now 66kg. It was increased a couple of years ago after many coaches were found to be overweight when filled with "average" passengers and luggage, though luggage shouldn't be a problem on an RML. Mind you, how many tinnies do your Aussie passengers take on board with them :) ?

But as roy says, check the pump is opening fully. sometimes you may have an air leak on the throttle dip valve if it's still fitted. On the Iveco engines, their problem is the linkage is set up wrong and the slightest bit of wear on the pivots will cause loss of power. I've dealt with several like that over the years.

Was your pump rebuilt to LT spec or Cummins spec? Mine was done to Cummins spec to 2400rpm and flies along at near lorry speeds and will go up Wrotham Hill on the M20 with little noticeable loss of speed when empty.

My bus number (if any): RML2532