Removing the limiters is usually necessary because even though the engine is "pre broken in", you will need to make adjustments to the needles that will usually require the limiters to be removed to accomplish. Removing them only eliminates the mechanical stops that prevent needle movement past a certain point. They aren't needed to make the plane fly, they were only there to prevent a major maladjustment of the needles when first starting out. They should be close to begin with, my first Evolution was too rich, and did require the limiter to be moved. I just ended up taking it off.

The limiters come off with a tiny allen screw that locks the limiter in place.