Well, I'm going back to a problem I was trying to diagnose last year.
Two different distributors (Rock Auto) three different modules, with varying results.
From no higher end performance, the original problem (stumbling on the upper band of the power range). Then complete R&R of the distributor and module with which resulted in worsening undriveable symptoms. Then I ordered another complete distributor with module and just changed the module that resulted in about 70% improvement.
Result, Stumbling idle when it warms up, and high end power loss. Intermediate power fine, highway driving fine, just not when you downshift lets say into fourth gear and stab the throttle, starts to hesitate towards higher end before you would shift to 5th. And I'm not winding it up towards the yellow arc or anything on the RPMs.
New cap, rotor, plugs, plug wires, coil, and injectors.