The heat riser is something that I haven't thought of checking. Good idea and thanks a bunch for your suggestions.
I replaced the plugs last weekend and drove it hard for a couple of miles. That was enough to show significant signs of carbon on 5 & 6 with it present on the insulator and the center electrode (but mostly on one side), as well as on the face of the body of the plug.
I've been really hesitant to crack open the Rochester B on it as it barely leaks at all and I was hoping to keep it that way. I'll probably have to break down and do it if I can't figure this out.
