as his is an early OBD2 car it most likely won't throw a CEL unless the event happens for a long enough time, or more frequently. If you DO get it to turn on the light, you can not only pull the code, but the freeze frame data(data on the other engine sensors at the time that the light went on) this data can be quite helpful determining what is going on.
For example, if the car had been running for a while and was warmed up, but suddenly the air fuel ratio was in the 9's and the coolant temp sensor for the ECU was reading -45, this will be your biggest clue
As well, not sure what you mean about base maps, but if you mean limp mode, depending on what is actually wrong, again, it might not if its not for a long enough time frame.
It may be something temporarily plugging the exhaust such as a broken catalyst substrate.
It could also be in the transmission possibly, something holding the engine back?
It could easily be a connection at a vital sensor like the maf or the ECU plugs being partially loose or corroded.
Without driving it, its hard to diagnose something like this.
