Pulling the ECM fuse will not do it.
The SRAM in the ECM is powered from a separate feed. There is usually a disconnect in that feed near C500 in Fiero. (Looks like the O2 sensor connector with Orange Wire as I remember.) If you can't find it disconnect the negative battery terminal. (ALWAYS disconnect negative first!)
The ECM needs to be reset any time you have stored codes. There is no other way to clear them on the older ECMs.
You do not have to reset the C3 and P4 ECMs after a sensor replacement but it is a really good idea. The ECM will update block learn either way within a few miles. It is better to just start with a blank slate and let the ECM sort it out from scratch.
BLM (Long Term Fuel Trim) and Integrator (Short Term Fuel Trim) are not fixed. They can and will change durring normal operation of the vehicle. They have to be able to do that.
BLM's name is related to various blocks of numbers in the fuel map. BLM will change in response to Integrator. The ECM will select the Block of fuel map that keeps the Integrator the closest to 128.
You will also have different BLM based in engine RPM and load. The BLM you get at idle may not (And often is not) the same you get cruising the highway.
Integrator changes almost constantly. BLM will only change every few seconds. Once it settles on a BLM it will stay there unless something on the engine changes. Example: If you induce a rich mix long enough, BLM will try to adjust for it. You can actually watch it do it on a scanner.
)
