I have an 87 L98 Iroc that is running lean. I have good fuel pressure and I sent the injectors out to be tested... all 8 tested ok. Also I did a code scan and received the standard code 12 and nothing else... no engine light. I also checked the Throttle sensor and its working fine (.58 volts closed and progressively increases as the accelerator is pushed). The car starts but pushing the accelerator does not seem to add any fuel. It appears that the computer is not increasing the injector pulses as it should. I was thinking that the ECM has a problem but it supprised me when it was able to display a code 12? Also I was think that maybe the MAF was the problem?
IP

 

Don't know if it's the same problem but thought it might help.
I had a problem on my 89 IROC where it would not "hot start", I would have to wait like 10 minutes to start it again. Eventually it would not start at all even after waiting. I was getting code 44 (I think) oxygen sensor lean - point was it wasn't getting fuel. After much troubleshooting (replaced ECM, fuel pump relay, a few ignition parts spent 8 hours at a mechanic friend's shop) it turned out to be the fuel pump relay connector. The wires were shorting out. Replaced the connector with a new gm part for like $40 and starts everytime now.

I still have a cold start problem where it takes too long to crank (4-6 seconds) if it's been more than a few hours since it was driven but that's something else, at least it starts Anyway, check your fuel pump relay & connector. Might be it.