I'm sorry to hear that you are dealing with my situation. I have a September build 09 and have been living with this lag for 18 months. Look at the sticky lag thread on the main page. It lists the latest software update (which is the third or fourth change since your car was built). I've been driving on this latest update for six days now and have not had any serious lag issue. However, every previous update has reverted back to the old behavior within a few weeks. So I can't say with authority that this fix is any better than the previous ones.
Mention SIB 28 07 08 to your SA along with a description of your lag. They should update your car with the latest software.
I personally believe that the transmissions have a lot of variability from car to car. Some of us are plagued by transmissions at the bad end of the spectrum. It may be the case that no software update will cure your or my transmission woes. Sorry to be the bearer of bad news.