I just did a bunch of "research" into it. Red hot is indicative of excessive fuel getting into the cat, accompanied with low power, unresponsiveness, etc.. multiple routes to causes from there: low compression/damaged valves (I have refurb headers, new valve springs/stems, new pistons and rings, so I can hopefully eliminate that), bad fuel pump or filter (we've exhausted that option), or misfire from bad ignition coil/plugs/wires. I am going to explore this option tomorrow. I put in an upgraded MSD coil last year long before the rebuild this last March.. may possibly not be the best fit for a 2.9l. I'm test that out tomorrow. These symptoms have existed and persisted before and after the rebuild, so we'll see.