Then I stick to my theory. wrong heat range for the new cam and all the cylinder pressure. Not saying this is "for sure" the issue, but I'd try fattening up the carbs and running RN12YC. If it doesn't work, your out a little time and a set of plugs. BECAUSE...……. cudafever's picture is your plug, then I go back to my previous statement, it looks blistered. You may find yourself adding some performance that will be noticed by the seat of your pants