Well the choice was clear for me today. During boost my car started missing and had a bad miss at idle with some smoke coming from the tailpipe. Upon inspection of the spark plugs (Denso iridiums) the number 6's porcelain completely separated as shown in the second pic.
Put the old NGK BKR7E's back in and its running fine again.
Put the old NGK BKR7E's back in and its running fine again.
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