Originally Posted by Clark Turner
The -11 at the end of the plug means 1.1 mm. Or 044 gap. This is for a non turbocharged car.
The NGK book catalog was printed wrong years ago and for some reason, they dont want to fix it.
You should never try to gap -11 plugs down to 030. The reason is the top ground strap (the part the spark jumps to) will then be at an angle leaning down. This distorts the spark and shields the leading edge of the electrode.
The correct and best plug for these engines is the NGK 2667. Never order plugs by the BKR7EIX number. Its very possible you will then get BKR7EIX-11 plugs in the mail.
Each weak I find several cars I am tuning have the wrong plugs in the 2.0 and 2.5 subarus. -11's will reduce the output power in a huge way due misfire under boost. In fact, they wont support more then about 12 to 13 psi before they start to act up.
Thanks for the prompt informational response Clark.