i have heard that it was a mapping problem
i think garage band is for the beginners so, no mapping program inside
i have midi pipe (a software)
i tried but no results so, i really don't know what to do waiting for a solution 
So, in fact all my packs from Toontrack are not at 100% because of that
i am waiting for a solution
Example: try the ROCK PACK _ EXPANSION EZX WITH EZD 1 or 2 (i have EZD 1)
with the VINTAGE PUNCH SNARE (the 2d preset) : it does not sound good= the drumstick does not hit the center but the sides (it sounds reggae, timbales )
when i program garage band to play just the snare drum +bass drum (without any cymbals together) i have the real and good one of the snare drum (like the in demos )
but just for this setting
if i want a rhythm with cymbals, it does not sound good for the snare drum
so, it is unusable