If she is running OK, and you have no uncomfortable seat-of-the-pants feelings, then it's just carbon buildup. Is this the first time you noticed it or is this the first time you actually looked and saw it. Whatever it is, in the absence of any other symptoms, I wouldn't worry too much, unless, there is something else that you are not aware of. BTW, this may sound silly, but are you sure it's your car?
[Edited by jeffsr on 12-15-2000 at 09:28 PM]
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.