Rich, If your car hasn't been tampered with a lot. Then a simple replacement of the 02 sensor will get you back to normal. If all conditions are perfect, then the 02 sensor is supposed to be replaced every 30,000 miles. But since we don't live in a perfect world you have to figure on replacing it sooner. There is lots of things that will make it run richer and or contaminate the 02 sensor quicker. To many to list or maybe I should write a book on it. Seriously, I would replace the 02 sensor and possibility readjust the 02 adjustment to compensate for wear and you should be OK. If it still persist, then the warm up regulator / control pressure regulator may be going out. John Hervey www.specialTauto.com << Gents, I'm also running very rich so I've been following this conversation intently. First question: The three brass set screws on the intake near the "W" pipe. Two are for the cylinder banks and are supposed to be fully shut. That much I know. Is the 3rd one the mixture screw? Are all 3 supposed to be fully shut? If not, how can I best determine the proper position of that 3rd mystery screw? I don't have sophisticated test equipment. Second question: The yahoo owner before me, cranked them down so tightly, that when I checked them, the heads snapped off all 3 of them with almost no effort. I presume that an easy-out or similar extraction tool will remove them....right guys?? Thanks, Rich #5335 >>