Improvement has been phenomenal I have them in my 1970 jaguar E-Type and the performance improvement has been phenomenal including better gas mileage. I don’t have but a couple of hundred miles on them but I sure like the additional performance they are giving me. Richard Russ, Verified Buyer Spark Plugs 5 2020-01-03T21:33:28+00:00 Richard Russ, … Continue reading Improvement has been phenomenal