With respect to the original topic, I still question whether the catalytic converter is working properly. Maybe it is not going into closed loop, and thus is leaving the mix too rich.
The cat is working as it does not show the extremely high HC at 2500 rpms when it has a lot more gases going through it.
Closed loop= i connected my meter to the sensor lead of the O2 sensor and it shows that its working and you can see and hear the minor variations of the engine as the computer adjusts the mix in relation to the readings from the sensor. and when i unplug the O2 sensor it runs really bad.
That is the only "test" for closed loop i can come up with.
The OP has replace the ATC and ECT sensors, but I wonder if it was the correct coolant sensor. I *think* it has two sensors. One for the 'gauge/idiot light' and one for the computer. If the gauge sensor was replaced, but not the ECM sensor, that could account for the extra HC's.
Got the right ACT and ECT sensor.( have two wires and fits the plugs)
I got the right sensor because i had to repair the idiot light' wire to get my gage working and know the difference,(has one wire)
I have talked to a mechanic that worked in a state where they did not smog test and he confirmed that some shops tinkered with the programing on ECMs to increase performance. His shop had the programmer and many of the mechanics did adjustment during tune ups to bring more business to there shop.
(In his state when they did start smog testing they made even more money replacing the ECMs to pass smog)
Since this truck came from a state and county that never smog tested there is that possibility, that is untestable as no one now has a program reader.
All i have left is to take the truck to a shop that can diagnose the problem as I have changed everything that would effect smog except changing the ECM.
I am not ruling out one or more of the new sensors i replaced being bad from the parts store.
But the truck runs fine and that even confuses things more.
I am waiting for my next disability check on the first of next month to cover the cost of the diagnostic testing.