A plugged fuel pressure regulator will make it run rich, especially at idle.
You can test the pressure at the T junction.

On 2/16/06, Geza Polony <gezapolony@sbcglobal.net> wrote:
>
> Just replaced the O2 sensor the day before yesterday. Old one was black.
> Now
> voltage readings from sensor are all across the board. No smell, no blue
> smoke, but a lot of carbon in the exhaust. I just fixed a couple of pretty
> big cracks in the vacuum system--maybe that will change things.
>
> What else would make them run rich?
>

--
Jake
1984 Vanagon GL
1986 Westy Weekender "Dixie"
www.crescentbeachguitar.com