What parts limit the engines RPM? Where are they located?

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The engine is limited to 4800 RPM. Idle is fine, and the engine runs great up to 4800 RPM. It seems like a rev limiter is cutting in too soon. The engine acts like all the injectors stop firing at 4800 RPM instead of at the red line. The engine will drop about 500 PM and start running fine up to 4800 RPM. No check engine light on, and my OBD2 code scanner shows that no trouble codes are present.