My 2013 QD 6000 looks just like the one in the picture. The manual for it covers the series up to the QD 7500. And it does speed up and slow down with load just as the "new one" does.
I wish that my coach had offered the 7500 had as an option, I really could use the extra power at times. The catch on the 7500 is that it has the same motor as the 6000 and being naturally aspirated it may not produce rated load at higher elevations. The saving grace is that you rarely need all of the air conditioners running at those elevations.
Incidentally, the engine came with a Kubota oil filter on it. That is fine with me, Kubota makes some great engines.
