i dont think you can go wrong with any of the kits
bd
cutler
twisted
ovs
contact them all and see what appeals to you!
i could have flipped a coin when i bought my kit,(2010 m8) but,,, i went with bd because of the ebc, and the tunnel dump, to me those were attractive features.
i know of other people with other kits (cutler,ovs,twisted) and they love them.
whatever appeals to you the most, will help make your decision....
again, i think all the kits are very good, each one offers something a little different, but to say one is better than the other, in my opinion, would be ignorant!!!!
i do think after owning a turbo that cold air intake is a must though, that would be high on my list of things i would want in a future kit for any sled!!!