The rev limiter seems to be in the distributor rotor, that limits rpm by dumping the spark on the base instead to the sparkplugs.
And it does this via a centrifugal weight that cuts/redirects the power to the base of the distributor if it revs to high.
I say "seems to be" because I found some contradicting information if it was in the ECU or the distributor, most ppl seemed to point towards the spring in the distributor rotor however.
I don't have any personal experience with this engine.
But the problem can be many-fold. Just because it doesn't rev higher does not mean that it is the rev limiter. It could be something else, like a worn cam, to rich fuel mixture, worn valve springs, the list can be made long.