if you fitted the body of the 996 throttle assy do you not have to shorten the throttle cable and turn it into a short action throttle ?

If you are going to use a 998 etc throttle grip +body you need to modify the bike from a twin cable to a single!
Ive done this and you do gain from a two grips from nothing to full throttle, or 67 degrees instead of 93!!

This is quite time consuming though.

The easiest option is....

to use the fast idle lever off of a 998, as it is indeed separate from the switch gear.