We never recommend replacing a catalytic converter without a complete emission system diagnosis first. Your Toyota pickup's high CO numbers indicate there is definitely a "rich fuel" condition which will require hands-on diagnosis. However, with CO numbers this high, if your Toyota pickup was producing the high CO long enough, it would have already damaged the CAT. So even after you found the real problem causing high CO you may have had to replace the CAT also.
Your Toyota's oxygen sensor should be inspected to make sure it is sending the correct voltage signals to the ECU (engine control unit). The ECU should be inspected to determine the oxygen sensor signal is reaching it and it is computing the data properly and sending the correct signals to the fuel injectors.
Additional sensors which must be inspected are the Engine Coolant Temperature (ECT) sensor and the Manifold Absolute Pressure (MAP) sensor. If the coolant temperature sensor is not operating properly (not sending the correct voltage signal to the ECU) the ECU will not be able to properly calculate how much fuel to deliver to the combustion chambers. When the engine is cold the ECM is programmed to deliver a richer fuel mixture (more fuel). As the engine warms up, the ECM will lean out the mixture. Insuring the ECT is sending the correct voltage to the ECM is important for correct air/fuel ratio (optimum is 14:7).
The MAP sensor is used to measure the amount of intake manifold pressure/vacuum. This sensor must send accurate information to the ECU as well, in order for the ECU to calculate exactly how much fuel to add to the air entering the combustion chambers. On a 1993 Toyota pickup it is very important to ensure the MAP sensor is working properly and that there are absolutely no vacuum leaks. You should make sure none of the vacuum lines/hoses are disconnected, broken or brittle.
If after an electrical diagnosis if it is determined the fault is mechanical, the locations which need to be inspected are any and all points of fuel entry, most predominantly the Fuel Injectors. It is not uncommon to a stuck "open" or "sticking" fuel injector to cause high CO and a rich fuel mixture.
