90% of the people i have talked to say the sparkplugs just go bad to fast..to some it seems like they have even lost power.....thnink of it this way...if you get a +2 or +4 plug, the spark is still only going to go to the cleanes prong with the most metal showing...so you think you using all 4 but in actuallity as time passes, you just using one.
Some call the fake plugs...I call them a waste of money...Get Motorcraft or Autolite Double Plats like suggested above....thats all i sue and im completly happy with them.
Roz