Spark Plug Gap – .024-.028
More Boost = Less Gap
100HP Over Stock = 1 Step Colder Plugs
2002-2005 Subaru WRX Heads:
Iridiums:
Stock heat range:
NGK – PFR6G
NGK – BKR6EIX
Denso – IK20
1 step colder:
NGK – BKR7EIX
Denso – IW22
2 step colder:
NGK – BKR8EIX
Denso – IW24
3 step colder:
Denso – IW27
Copper:
Stock heat range:
NGK – BKR6E
NGK – BKR6ES
1 step colder:
NGK – BKR7E
NGK – BKR7ES
2004-2007 Subaru STi & 2006-2007 WRX Heads:
Iridiums:
Stock heat range:
NGK – ILFR6B
Denso – IKH20
1 step colder:
NGK – LFR7AIX
Denso – IKH22
2 step colder:
Denso – IW24
3 step colder:
Denso – IW27
Copper:
Stock heat range:
NGK – LFR6A