Good point about the 8 year interval.

An ignition tester should be able to verify that system is up to snuff, along with flow testing the fuel system(electric pump) to make sure it’s keeping up.

At this point, it makes sense to perform those tests.
But the motor not wanting to get past 55-5700 or so is pretty much par for the course with those cams.
You’d basically be verifying you don’t also have another issue to contend with.

Frankly....... the drop in performance with the new cam/intake/carb is pretty ugly......imo.