98 breeze still chugging along

Can somebody give me suggestions? I have a 98 breeze that is still making it down the road, barely. I noticed the end of the tailpipe is now covered with black soot. Inside the pipe and about a half inch back on the outside, didn't use to be there. What would cause this? It is running a little rougher with a little worse mileage, together or coincidence I don't know. Thanks for some help.