I'm still fighting with the slow throttle response on my 87 Iroc, 350TPI, 57,000 miles, etc.. Its all stock. I've replaced all the filters, plugs, cap, rotor, coil, etc... The volt guage reads 8volts at idle. I've installed a new battery and I've tested the alternator about 3 times now in and out of the car. There are no codes, but I do get the code 12.

So any suggestions?

Add ignition module to the list also... The alternator was rebuilt once to correct this problem, then it was replaced with a mid-grade remanned alternator...

I think I'm going to try another GM alternator next unless anyone has a suggestion or two.

Did you confirm the voltage??? Test the output and don't rely on factory guages. If your actual voltage is in the 8 volts range your ECM will add more fuel (its in the programming). Get the voltage issue figured out before you go tossing money away on parts you may or may not need.

Hehehe money... on parts... hehehe... Don't worry all the diagnosing today didn't cost anything... its all the glory of having so many spare parts I can't turn around in my garage. But anyway...

I figured out that the audible warning box (seat belt/key/headlight buzzer) was removed. It didn't fix the problem, but it made the car feel more right.

I fixed the throttle response issue by swapping in a different ECM. The volt meter still reads low, I'm going to start testing with my digital volt meter tomorrow to find out if the alt is bad or what's going on... How do I isolate the alternator to determine exactly what its charging in the car?

You can check your voltage right at the alternator. Test the voltage on the lead that goes to the battery. Voltage should remain above 13 volts at idle. Do you have any way to datalog???? It would be interesting to see what the ECM is getting for voltage as compared to the output of the alternator. If for some reason the ECM is not getting the correct voltage then thats a problem.

I haven't got anyway to tap into the ecm other than the paperclip... maybe an auto Xray if I take a short drive.