I think it will provide a benefit above 400whp because you can open the gap and have a stronger ignition spark. You will have more power in midrange anyway.
Here is a N54 dyno comparison at 180 load, .018 gap with sock coils (red) and .022 gap at PR coils (blue).
View attachment 48795
The B58 coil provide more energy as the PR coils, so the effect will be bigger and the gap can be open to .024 at the above example I think.
When I receive the B58 coil kit I will post logs with Stock coils comparing to the B58 coils, with same tune and boost settings.
what is the boost level in this dyno ?
I was thinking of more in the range of 0.026-0.028” @ 25 psi with the b58 plugs since it has a smaller core.
It would also be interesting to see how it performs with IGR enabled.