From what I have read and heard the most recommended replacement pads for the stock calipers are the Porterfield pads.
The part numbers I have written down are AP-63 for the front and GD-535 for the rear. These are the R4S street pads and run maybe $200-$250 for the set and are by all accounts a big improvement over stock.
Do a search to find out more info, there was some discussion that the rear Porterfield's need a small modification as they don't have the notch in the back to stop the cyclinder turning.
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