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

[wby300]

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?