Subaru Imprezza Sport 2006 (automatic) acceleration

Whether from full stop or while in motion, acceleration may be nearly zero, or the car may actually slow, for a second or so when trying to accelerate. To my criticism about this to the local Subaru dealer/shop, they say (referring to a previous model year) that Subaru “is sometimes very slow about bringing out a firmware revision to correct this problem”. So when will we see this “revison” for the 2006 model? And why do thy tolerate such poor performance to begin with?