I'm w/ Dwight ^, stick to premium its what the owners manual calls for on our turboed cars.
Quite frankly why risk detonating our cars w/ the reputation that we have?
If i have the ability to run a higher octane i do, i'd rather sacrifice some throttle response for safety once my car is in the 140+ KPA's (positive boost)
P.S. I dont know how octane ratings would have an effect on your clutch feeling softer, I agree, its just you.