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Splash Man is right about staying away from the +4. I have run the Bosch before, and did not have any problems with them, but the +4 are not worth their claim.
I run Motorcrafts now and have been with no problems (I can get them cheaper than the Bosch's - about the only reason). They work great - even with all the MSD DIS4, MSD coils, and added power...
I am wondering if the bosh plugs work better in the newer explorers say 95 and up. and in the V-8's. I use bosh in my wifes MB and they are great but in my explorer they were well not so good. I also wonder if there is some correlation to the particular wires or ignition system that is behind the plugs making the bosh work well for some and not for others.
And good plug wires, like Jacobs 8.5mm wires. Accel also makes good wires. Definitely get 8mm or above size thickness. You'll get more of a performance boost out of performance plug wires than you will out of spark plugs.