[100IH]

And are the plugs fouled from the MMO? Stay on point, don't try another fix that is not next thing to verify. You need to verify spark at those 2 plugs, common possible cause: crack in cap causing cross-fire, Wires crossed (may not apply), try swapping the rear plugs with the front plugs. Then consider one intake port feeds #1&#2, vacuum leak at manifold gasket.