There seems to be some question as to whether this is actually an upgrade or not, but I was putting in a CJD Super Shaft anyway, so why not? The factory engineers must have some reason to have changed the design. I ordered the 2009 impeller and cover, and the "long" Super Shaft from CJ. The long and short shafts are really only about 1mm different in length- I expected to see a thicker impeller to match the longer shaft, but................. The 950 pump cover. The arrow shows a reference point to gauge the height of the cover- I was surprised to find the 990 cover actually had less deck height than the 950 part- Because the 990 impeller is actually thinner than the 950 impeller, even though it's hub is 1mm thicker- So where is the improvement over the old pump? It appears that the 990 impeller has anti-cavitation style vanes, typically more of an improvement at higher rpm- If there is any benefit from the 990 pump, it will probably be undetectable, but it's always interesting to try something different. I'll admit to being a sucker,(when I was younger and more foolish),(well, younger anyway), for an ad that promised "Up to 10% More Horsepower!" A friend who does Ducati dyno tuning pointed out that such an ad really doesn't promise anything, except that you won't get OVER 10% More Horsepower. Some day I'll learn.