Would appear not a lot! Nothing related to performance anyway. 1198S Ohlins Forks - Ducati Superbikes
Without going to gas forks, upgrading the piston valves with a KTech SSK kit is a great improvement for any set of forks. Get the oil moving at the right rate first. A full on cartridge kit replacement is worthwhile if the shocks are much older.
Ive just fitted some ohlins to my 848 but noticed they are the fg811, so 1198s not 1098s. See how I get on with these first . Also same forks are fitted to the R and SP versions so cant be that bad
Standard Ohlins internals are pretty average. Get a 20SSK fitted with some lighter weight oil, and you'll see a very noticeable improvement in both the primary and secondary ride.