[Elwood]

I think I'm on the same track Al, but the HT 4100 runs a TBI so I'm wondering if #4 & #8 are adjacent to where the EGR dumps into the manifold or the air pump may have some affect on the fuel mix making it harder to generate a spark in those cylinders????? I've already closed the gap on those two plugs 0.010", maybe I should go another 0.010"??????