Hmm. Gearing differences? Dragging brakes? Worn chain? Duff battery? It's a bit difficult to diagnose from a distance!

If all the above check out ok, then I'm incluined to start swapping stuff like the PGM from your frinds bike to yours...

Oh, just one thing, maybe his bike has been ported by the previous owner? Have you had them both on a dyno to check the power outputs?
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