Glowing Headers

Your back cylinders are running leaner than the front cylinders. Timing effects all the cylinders. The problem is not that you have glowing headers it is that you have some cylinders leaner or richer (depends on how you want to look at it) than the others. I have had more than one car after a highway speed run have the manifolds or headers glow at night. But the glow should be even and is OK as long as the motor is not too lean. Like mentioned earlier you most likely have a fuel distribution problem.

Chuck