ECM has no idea if the cats are there or working. It will not affect anything.
Does the fuel mix change if you remove the belt from the smog pump ? If it does, the smog pump control system is not working correctly and its pumping air into the back of the heads constantly. That makes the O2 sensor read lean, and it adds fuel to compensate. Pull the belt and see what happens.
Does the fuel mix change if you remove the belt from the smog pump ? If it does, the smog pump control system is not working correctly and its pumping air into the back of the heads constantly. That makes the O2 sensor read lean, and it adds fuel to compensate. Pull the belt and see what happens.
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