Just thought I'd share about my 97 Blazer.
It's been a bit difficult to start for perhaps a month; mulitple tries, and it would "shake" for the first 30-60 seconds of idel then smooth out. Drivability was OK.
Then started seeing the SES light come on in the last week; then the SES light flashed a few times at the start of a trip.
So, off to the repair (non-dealer) shop. Misfire on 5 & 6. Replaced: Fuel filter, PCV valve, distributor cap, rotor, plugs. "Injector service". Now it starts and runs much better - probably help the gas mileage also. So far (1 day out from the repair) no SES light.
There are about 125k miles on it. At 50k the plugs were replaced, so it was probably time for other stuff.