Hi Phil,
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Avoid cheap electrolytics like the Plague.
See Amarin's nice write-up with details about his ECU rehabs.
You need the best long life caps you can find for ECU's.
I hope to do my ECU's later this year.

Spook has a good idea about servicing connectors.
Check the impulse sensor (They don't call it a CPS) above the flywheel.
It provides the engine RPM signal to the ECU with a pair of wires shielded and a ground. see if the harness looks OK.
I use a stiff toothbrush and 90% isopropyl alcohol to scrub out connectors,
then blow out with air, add a little dielectric silicone. Beware using strong solvents with connectors, I think that can damage bullet style connectors, such as the OBD port connectors.

I'm still wondering you have an RFI problem:
Try wrapping aluminum foil around the shield of that sensor harness and see if it changes the RPM limit. The foil will cut unwanted RFI pickup to the harness.
Service the knock sensor connector too, you don't want corrosion in connectors. That's another key input to the ECU. If you lose the knock sensor signal the engine timing is retarded 10 degrees.

Good luck, Bill