I hear about that plug on the mixture, I have 3 carbs and I have yet to see that plug. The idle was bad so I tried to adjust the idle screw didn't work, so I tried the mixture and I F'd it up worse. Then I took it to my mechanic who adjusted the thing properly. Now it is still running too rich which 3 mechanics including a carb shop said means I need an overhaul. I priced an overhaul at $392 dollars so I can get a weber cheaper but I want to be sure it will not put out rich readings too otherwise id rather just rebuild this one.