2001, one precat is getting red hot.

I had everything pulled apart and noticed one precat was completely hollow. So I ordered a new unit, installed it and now after running for a few minutes the same precat is getting red hot. This of course explains why the old one was hollow, but why is it happening in the first place? I have not gotten any codes before this or noticed it running poorly. The only thing that has been an ongoing issue is it gets bad heatsoak(I assume) and will not start when it gets real hot.

So far I have swapped injectors from bank 1(precat is fine) to bank 2(precat red hot) and the problem did not move with them. Any other ideas on this?

I should also note that I replaced all 4 O2 sensors with new NTK ones and the problem persists. I do notice black soot on my tail pipe(which is also fairly new).

Is tge muffler plugged?

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No. Muffler and tail pipe are 6 months old and in new condition.

One or more injector might be leaking, causing a rich mixture that may in turn cook the cat. You may have a bad spark on one or more cylinder such that unburnt fuel is cooking the cat. Worn rings or valve guides may cause oil to get in the cylinder, which in effect is a rich mixture, again cooking the cat. make sure your spark plug wires are going to the correct plug, if mixed up you may get a lot of unburnt fuel in the cat

First thing Id do is look the spark wires and confirm they are going to the correct plugs, then look at the spark plugs, all six of them, and see if any has signs of rich running, or oil on them. that may pin point which cylinder(s) are the culprit. from there you can test the spark, make sure you are getting a good hot blue spark. check the ohms on the spark wires if spark is weak along with the cap.
if spark is good, then look at the injectors, remove them and test for leakage, spray pattern, flow volume.

If the plugs look oily, a leak down or compression test might find bad rings, if all that is good, and you got oily plug(S) then suspect valve guides.

of course if you are driving for testing, get that nice new cat out of there and replace with the hollow one so the new cat is not damaged

good luck, let us know

Sounds like a fuel delivery issue.