I'd put money on it, that this is problably the case....as I've had this happen before and had the same result.
In the exhaust business, every time a customer came in with glowing red exhaust pipes it was caused by excess fuel (too rich) The unburnt excess fuel continued to burn in the pipe after it left the cylinder causing it to turn red. I replaced lots of melted down cat. converters from excess fuel. The glowing Y pipe was a sure sign. One customer came in worried about his cat. He set the choke and left it to warm up in the winter. He got tied up for a few minutes and looked out the basement window to see the glowing red hot exhaust. After he kicked it down off of the choke the exhaust slowly lost the glow. It didn't last long enough to damage the converter. I'd suspect a too rich condition on the red side.
The Jalopy Journal
