I HAVE A 2015 PITSTER PRO DOUBLE X 600. WOULD LIKE TO UP THE PERFORMANCE. NOT HAPPY WITH STOCK PERFORMANCE. ANY ONE KNOW OF ANY UP GRADES AVAILABLE AND WHERE.

personally I would upgrade the machine itself, to a 800 twin, they spend a LOT of cash/time on testing/design etc,on  these machines before they go into production, in my experience, (not always me) but once you start messing around with things like power delivery, performance etc, that's when things are never the same again with that one machine, power restrictors are there for a reason, 99% of the time its to protect the machine, not to stop you going too fast.
all the best with it.