When I was sixteen I had a 78 Mazda glc with a 1. whatever in it. Went and spent money on some Bosch plus fours(i think they were just released back then), installed them and went for a ride. The car ran like shit and stalled intermittently. The head tech at the dealer(friend of my fathers) told me to ALWAYS run what the manufacturer recommends. I swapped those out for a new set of OEM specified plugs.....voila, car ran great. Imagine that.
