Besides fuel mixture issues don't forget this one
One more thing that has caused header pipes to glow at low speed is an over scavenging exhaust system. This is most notable when tri y headers are used like some circle track engines do. Glowing pipes at idle is very common with these set ups or ones that scavenge in this manor. The over scavenging pulls much of the in coming intake charge into the exhaust. This happens during the valve overlap at low exhaust velocities, and this condition corrects itself when rpm and exhaust gasses speed up at higher rpm's. If you have a conventional 4 to one collector your are not likely to have this happen but if you have the 4 pipes merge into two then into one at the collector this issue is very common. Flowmaster made a gizmo that slips over the 4 primaries and merges them from 4 to 2 to one in about 24" that over scavenges at idle .
More food for thought
Bruce