I'm assuming your octane level is measured in RON. Why are they discontinuing 95 ron gas? (thats 89 aki for us in north america)...

BMW reccomends 89 aki, but I've used 87 for a while and never ever had a problem. I's probably opt for a higher octane gas though than a lower one.

Nothing needs to be adjusted for 98, but I'd just just chip it since you'll be using 98 anyways...might as well take advantage of it.