[jhv48]

If that were the case, he wouldn't have spark at the spark plug. Which he says he does.

Start with the simple things first. Weed out the variable (additive) and go from there. If you get spark to the plugs (and no one has screwed around with the firing order) then it's a fuel problem.

It's always something simple!

How much Sta-bil did you add? One ounce for 2 1/2 gallons of fuel is recommended.