I'm embarrased to admit it but I really haven't checked the car out yet. I just now went outside to look at the exhaust tips, and yes... they are pretty sooty. I'll check the exhaust smell during my lunch break and go from there. Assuming it's running rich, would would the probable causes be? O2 sensor(s)? When the O2 sensors on my Z31's went bad the car would barely idle and not rev past 2000 rpm.