[surfbeast]

soot in the tailpipe is normal, unless were talking LOTS of soot. Unless your smoking out the tailpie it should be fine. I like to watch and smell of the exhaust periodically to see if I notice any changes in color/odor. It sounds like you may need to change or clean your IAC. My car did the same thing and I cleaned it with brake cleaner and it has run fine since. Also check all the intake/plenum conections for lose or cracked hoses.

Happy Easter!