i did the onlins front springs... kinda unusual for a Duc. they are stiffer than stock. .90's. i did the racetech Duc ST valves. well... i had Mark Sutton at the ducshop.com install them. he will know what to order. they are the FMGV S2043 models.
here's a old quote:
"mark @ the ducshop did my forks. here's what i think... run and buy the gold valves for your S4! the difference is night and day. no more high speed pogo/chatter. you know how your windscreen on your S4 flops around? after the valves, almost completely still (except for the wind pushing it around). i did ohlins springs and 5wt ohlins fluid.