Spark plug gap , boost or octane a consideration?

I'm trying to determine the appropriate spark plug gap for an BMw N54 build. Most advice seems to indicate that required gap is a function of target boost levels, gapping down beyond .022" perhaps into the 0.018" for boost beyond 15+ PSI or so.

BMWs stock gapping is around .028" and many 'sources' indicate that below 15+ PSI 0025" to .028" would be okay, however others are saying I should reduce down to 0.022" as I'm running 92 (US) /98 (RON) (mostly E10 mix actually)...

Help please! Too much FUD around on this :D

Comments, rather than definitive.

Normally one would decrease the gap as boost increased, as it takes more voltage to jump the gap, but a smaller gap can cause ignition problems with light throttle - leaner and less dense - charges. You will need to see what your particular setup requires - you may not notice a slight misfire, but if the lambda seems to be leaner than expected, it may be due to a misfire allowing un-used oxygen through. If adding more fuel doesn't affect the lambda, it is almost 100% due to a misfire.

You will probably need to go a couple of heat ranges colder, too, but that will be a case of experimentation - start with too cold and if it fouls go one range warmer and retest - don't start with OEM as if it's too hot it could cause pre-ignition and engine damage.

Fuel octane shouldn't make a difference to the gap, but not 100% sure - anyone?

Thanks!

This echos exactly what my reading has told me. That for the boost levels I'm expecting to run < 15 psi that a .028" should be fine.. as this already seems like a fairly small gap to me. On the N54 many folks naturally go down to .018" when running over 20 psi. I feel (based on not much admittedly) that going from a factory 8psi to 10psi peak to a in practice between 13-15 psi , probably doesn't warrant going down to .022" . I am going one step colder on the plugs, but I think for these power levels even that might be marginal. I plan to check the plugs for fouling to ensure I'm not actually too cold.