The material the head is cast from don't know what material the center electrode of the sparkle plug is made from....nor does it care.
You can use platinum plugs if you want, but it is NOT mandatory....someone is just trying to sell you higher priced plugs....that's all.
The fuel filter should be on the passenger side, bolted on the inside of the "frame", just behind the pass side front wheel. You'll have to jack the car up to get to it. Be sure to use jack stands before getting under the car.
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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"