I'm going to ask my local dealer about this upgrade cause I want it.
I've got a new'ish car (Jan 13 build) and it's got a substantial torque slump between 3500 and 5000 rpm, which (sort of) fits my schitzo personality - either cool puttering around under 3500 rpm, or the other "me" that's in my second childhood and loves the redline. But I'd rather not have the flat spot.
The flat spot is maybe even more in my face because my daily driver is a turbo Forester, and it pulls like a train from 3000 rpm and I don't have go down 3 cogs to get some action...