I've run both copper core and iridium plugs in my SR20det, given the choice NGK iridium all the way. If i'm in a pinch Copper core NGK always get the job done they just don't last nearly as long as the Iridium core plugs.
S14 sr20det E85 16g turbo 19psi R35 coils
BKR7e I run .029"
BR7eix-11 I will leave them at the factory 1.1mm gap (.04") and they don't suffer from any spark blow out.
While i ran OEM SR20det coils i was gapped WAY down to 0.019" and it still struggled.
While i ran OEM K series coils i was able to get away with 0.025"
here is a helpful article for choosing
SR20det spark plugs including the correct hear range, what gap to run and other coil options.