Installed new Cat, and replaced Exhaust, puff of black smoke
 

Hi, I just installed a Cat, and replaced the exhaust with a 2.5" Aerospeed by itself, it runs great and but i noticed that a slight puff of black smoke when i hit the gas, to in park, to hear the exhaust? It also smells alittle rich when i start it cold? Be changing the exhaust to a much greater flowing system would i need to adjust any fuel or air mixtures? Or will the cars computer adjust itself?

For an older car like my own. Whenever I try to mod it, right after I cut off the power by taking the battery terminals off and let the computer just kind of drain and "forget" everything. Then plug it back in and the computer senses the changes and adjusts. It won't sense the changes until you do this.
btw, what year/model did you do this too?

Oh yeah, let it "drain" for 30min

Thanks i am trying that right now. Oh and it is a 1988 260e.

As I recall from my old drag-racing days, anytime you make major modifications to a car's exhaust system (headers, free flow mufflers, different diameter tail pipes, etc) you will probably have to adjust the fuel/air mixture. Hopefully your on-board computer will do the job for you.