I have a 1990 Honda Accord EX with 217,000 miles. Started hesitating when accelerating and the tach jumps between 2500 to 4000, all over the place. I can feel no difference with the engine. Replaced the ignition mod, distributor cap. Not getting any error codes and no CEL light on. Thinking it might be the coil, or maybe the distributor housing unit?

I recommend replacing the Ignition Control Module (ICM) and coil together. If the problem persists, after installing a new coil, you'll have no choice but to replace the distributor housing (genuine Honda only). Was your ICM brand new?

Yes, this was a brand new ICM, matched to the manufacture.