Service engine soon light, oh my god

[Tim]

Hello fellow members, I need your help. Last weekend I took my 90Z (basically stock DRM chip and 4:10s) to an 1/8 mile drag strip. Drove the car up there, approximately 100 miles, and topped off the fuel tank with 6 gallons 108 octane gas and made five runs. The car ran fine, just could not get traction. Anyway, after my runs watched for a while, hopped back in my Z and cruised home. Everything seemed normal and the car ran fine. We made two stops on the way home and every time we proceeded again the car still ran just fine. Got back to Bismarck and stopped to visit with some friends for about four hours and then decided to take the car home. We started the car and it idled rough with black smoke out the exhaust. As soon as I touched the gas, the idle picked up, exhaust cleared up, and service engine soon light came on. Drove my baby home about eight blocks and it ran okay but the service engine soon light stayed on.

The following morning I went out and started it several times with the same results. Started it without touching the gas and it idled very rough with black exhaust smoke, tapped the gas and it goes into high idle and the exhaust clears up and then the service engine soon light comes on again.

Does anybody have any idea of what is going on? I hope I didn't hurt my baby, baby, baby.

Can anybody also provide a link to where the instructions are as to specifically where and how to check codes and what they would mean?