I see apr has released a chip for the S4 V8 4.2l
 

They are claimng a draw-dropping awe-inspiring 11hp on 93 oct. 11 hp for $600 which is both disapointing and not good value.

I'm really quite supprised that our 4.2 V8's cannot do better. It looks like adding four more pistons is going to be my upgrade path when it becomes available mid next year.

Not suprising - N.A. engines don't usually have much to give without cams, exhausts, etc.
 

Given how few people are willing to trade their engine warranty for 11 aftermarket horsepower, $600 is the price to cover distributing the not insignificant development cost.

In an S4, you'll sell a bunch. The A8? Most are 'old' enough or conservative enough or wise enough not to trade their warranties for a few relatively meaningless ponies...