This is VMP's recommended spark plug for modified 5.4 L / 5.8 L GT500 and 4.6 L Cobra.

Must properly gap before installation.

Set of 8 colder spark plugs for a forced induction application, must be gapped at 0.026- 0.028" between 21-14 PSI of boost, over 21psi gap .024-.026"

NGK Iridium TR7IX 3690

NGK TR7IX 3690 Spark Plugs for Cobra & GT500 4.6 L / 5.4 L / 5.8 L - set of 8