All about the Roland Jupiter-series

I was wondering if anyone knew how to adjust the master tunning of my 
JP6. I have to turn it all the way counterclockwise in order to get it 
in tune.
I am also looking for a way to get a new sound set into my Jupiter 6.  
Does the MIDI receive sysex messages?  It is my understanding that the 
MIDI only responds to on/off messages.
thank