RPM governor

The PCM is the REV limiter. You would need to swap to an aftermarket PCM and tune it to eliminate a REV limiter. It's designed that way to protect engine from excessive RPMs. Stock PCM can only take factory presets. I don't think your symptoms are related to the PCM. Maybe transmission or clutch related.

It's not trying ti limit high RPM. It's like it's trying to prevent too low of RPM. Someone once said it was a feature to prevent the engine from stalling from too low of RPM. It is more pronounced with the AC on. It wants to keep the RPM up over 1000. By the way I forgot to mention that my S10 is a manual transmission.

I see what you are saying. Engine braking downhill and engine occasionally revs too high forcing you to use brakes to slow down. I don't know what shape your engine, transmission or clutch are in so can't comment on those, but one potential factor causing a spike in engine RPM is a vacuum draw, the engine is attempting to provide vacuum for something and has to boost RPM to make it. Or conversely a vacuum leak is allowing unmetered air into intake during engine breaking and PCM increases fuel to compensate. The increase in manifold vacuum (first due to engine braking and then possible leak) may be causing the engine to surge. Try going through the intake systems, clean everything and look for any vacuum leaks. Everything is suspect, PCV, EGR, all hoses.