This usually occurs if the car hasn't been driven in over a day. But if Im driving it every day. I don't get the smoke at startup. Unsure if it's oil or fuel injection smoke. My tail pipes are pretty sooty too. I don't get any smoke at idle or when I punch it down the highway. A time to be concerned or could my car could be just running a lil rich? It's a 98 Z28 and now 110,000 miles.

 

It's hard to say for sure but a lot of older motors show a small puff of smoke on start up because the valve guides and/or seals get worn and a small amount of oil runs into the cylinders after shutdown.
If you are really concerned about the motors condition go to a good shop and have them do a leak down and a compression test. They will then tell you what kind of shape that your motor is in.