Cool info Stephen. However the plugs are defiantly not the problem. Those plus 4 plugs are what you get if you walked into a dealer. The part number is on real oem as the high performance plug. Ya you might get a lil better performance from an iridium plug (I don't race my X), but they don't last near as long.... I have plus 4 in 4 bimmers now with zero issues.

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2001 E53 4.4 Alpine White, Sports Package
2000 E36/7 2.8 5 speed Bright Red w/ a HT!