Struggling at high rpm above 6000

What is the limiter set at? They come in pretty early. What cam! Hydr/solid? Status of springs? Age? AFR gauge will cut down on the possible causes. If its lean, fuel supply. Rich, could be ignition. Varies considerably. Valve train. When I spin mine to 6700 it just stops pulling. Doesn’t act up, just no power. More info needed