Does anyone have dyno data showing the benefit (or otherwise) of just changing the surface finish on intake manifold runners, or cylinder head intake ports for that matter?
It is important mostly in an intake manifold.
It isnt everything though.
Consider it to be that last 15 horsepower and a motor that's already had everything done and thought of that you could possibly do to squeeze the last bit of power out of it. Nothing wrong with putting the effort in but it's similar is to buying $1,000 oil pan for your street car.... along with .850 wheel roller lifters...
It's only the difference between winning and losing if you're at the top 2%