The header is glowing? Some things that leap to mind include a restriction in the exhaust, the valve clearances are off and combustion is happening outside the cylinders, perhaps unspent fuel is igniting in the exhaust when it gets O2.
Dragging knee is for the track, and dragging tail is for the lot. --Kane Friesen
When you're in a car, you're watching a movie; when you're on a bike, you're in the movie. --Robert Pirsig