[skidlids]

I would suspect there would be gains to be had, but as you say they will be in proportion to the production tolerance. Maybe JHP has got a few examples/dyno graphs he could quote/show you.
If IanH reads this he may be able to offer some advice as he runs a 998S in Superclub etc with winning results, I know he has bored out injector bodies but no idea of the full spec.