Bob Parmenter is correct to ask about the soot.

1. How long have you run it?
2. What kind of carb is on it?
3. What has been changed on the fuel pressure system?
4. Were the floats set/checked?
5. Are the intake ports sooty too?
6. Is the intake manifold stock?
7. Who put the intake on?
8. What did the plugs look like?

mike in tucson