I've just fitted one to my backup Ego 7. (only did it because it came without a bolt when bought, and the cure bolt from my kitbag spares poke out the back - awful look!)
TBH, hardly noticed any difference- it sounds different but not quieter necessarily. Not shot enough to notice any change in efficiency, but I doubt there will be any.
If you want to upgrade the bolt, a Cure 4 would seem a better call IMHO?