The last set of plugs I used were Champion RC12YC. They are copper. I have used Bosch 4 tipped before. They are a waste of money (lol).

Here is some more information that I remembered since posting the original thread. At one time, it was just the #3 cylinder that was fouling the plug. I do believe that the plugs are gas-fouling, as the engine does not burn oil at all. There is no smoke coming from the exhaust that I can tell. I purchased one new fuel injector, but did not install it myself. When I had the MAF installed at the rip-off dealer, I think he changed the fuel injector. However, I cant say that with 100% certainty.