I bought a 89 IROC 5.7 a few weeks ago and yesterday the Service Engine light came on and stayed on (with engine running). Is this light triggered by mileage or date, or does it indicate low oil levels (oil is clean and level is okay) or is there something else I should be looking for? Unfortunately I don't have a handbook to tell me and these cars were never sold new here so there are no dealers to ask. I am new to TPI cars, having always had a carbed Z28, so have no experience with them. Hopefully this is posted in the correct forum.

That light is triggered by one of the computer's informational sensors. It's saying that something's not right.
Do a search on SES light, checking trouble codes, engine light, etc. There's a procedure for getting the code number which you'll find.
Once you have the information that your car is trying to give you we can give you a hand.

Thanks for that. I don't know if it was because I was just shifting it in and out of the garage, but I gave it a run today and the SES (finally worked out what that meant) only lights up when the ignition is turned on then goes off when the motor starts, so I am hoping it has fixed itself. Plenty of information about the subject as you suggested, so next time I will be all set to do the paperclip thing.

Off subject a bit, but I have only ever had carbed cars - what is the best procedure to use for starting TPI cars, both cold and hot. I have to pump like mad on my '84 Z28, but have heard that you should not touch the gas pedal when starting TPI cars. Is this correct? I wonder if you would tell me what way you have found works best. Thanks again.

Fuel injection doesn't require you to pump the pedal at all when starting.
Clear Flood Mode is a different story but has nothing to do with every day starting.

I usually just wait the 3 seconds that it takes for the pump to prime and then finish turning the key.