Which spark plugs?

ive seen people run bpr7es plugs upwards of 25 psi with pump gas (93) just gap em right

 

[Wizardawd]

Ive seen 28psi out of a 14b on a stock fuel system also...doesn't mean it was right, nor lasted long.

Gap has nothing to do with the numbers. Gap changes are only necc. depending on your ignition system and boost level. Highest boost usually means a smaller gap to prevent blow-out. However, a larger gap always makes more power. Upgrading your ignition system will allow you to run larger gaps without killing the spark.

The reason for the different plug numbers is the heat range. Too hot of a plug and you'll experiance knock, high combustion temps and pre-detonation. Running a colder plug allows a slightly safer range before these things occur.

Wiz

 

[Hertz]

The major sacrifice for colder plugs is they have less ability to zap off any carbon deposits, and can get fouled quicker.