Well, after a week after I replaced my spark plugs / wires (last month is) I got great gas milage (442 to a 10 gal tank in my EK) Ever since then, my performance gas milage has gone down hill. I get a oil change regularly, change my air filter... so I figured I might as well check my plugs. Well, I check them and all of them look simular to the below picture. It has some kind of 'soot' on it and I've never seen that on a plug before. Is that common / normal?

Also, what are some other things that I myself can check to see what may be causing the performance problem.

I'm out in brandon now, and would like to replace the plugs with some NGKs, any suggestions on where to go?

Thanks!