[roflwaffle]

My friend's dad has a 90 GM pickup w/ a 350/TBI in it. It also has 307 heads instead of stock. For whatever reason, when a lot of load is put on it, the temps would go sky high and power will drop immensely. On one trip, it was noted that the DS manifold, the one w/ the O2 in it, was glowing red, while the other one (no O2) was still the usual color. He was told it was the "cat" although IMO whoever said that is just trying to rip 'em off, since the manifold that was glowing was farther than the cooler one, not to mention if a cat was plugged up enough to make a manifold glow, it would probably blow out the honeycomb pretty quickly.

The only thing I can think of that would cause this kind of issue is obscenely off fuel maps compared to air. I've read that in the event of a vacuum leak, OBDI and older systems with two banks will run proportionally richer or leaner if the other side is off. I've also read that way retarded timing can cause this, but wouldn't both manifolds glow if that was the case? Any other ideas would be great!