1989 Jaguar XJS wont pass smog check

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1989 JAGUAR XJS
V12
2WD
AUTOMATIC
98,000 MILES

I'm having trouble getting a Jaguar I just bought to pass smog. The tech say's it's pumping too much fuel way too rich. The tech say's maybe it's not coming out of cold startup loop mode. I did a full tune up myself changed all filters, replaced the fuel pressure regulators (2) and also replaced two of the cats. It still will not pass. I have been told that the computer may need replacing. How can I tell if it's a bad computer? Is the one I have adjustable I heard some are, mine is a DAC 6337 LUCUS 16 CU CONTROL UNIT 8478B with a date code of 4588. The unit does have a hole on one side with what looks like a recessed stainless steel rod? If the one I have is adjustable how do I do it?

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This computer is adjustable, but you have to have a special machine to hook up to watch the mixture. Chances are it is ok. Is the car getting warm enough. A bad thermostat can cause a car to run rich, also remember your car has two thermostats and if the coolant temp sensor is bad it too will cause fueling problems.