The idle needle isn't "lean". It's just set where it needs to be to get your engine to operate properly. There is no such thing as setting a needle "too lean" or "too rich" if the engine's running the way it should be. We've had engines with main needle valves at 2 turns out and at 1/2-turn out and it's just how that particular engine needed to be set. The actual position of the needle is irrelevant when the engine's running as it should.

HIgher fuel pressure may require you to turn the needle in farther than if you have lower fuel pressure. However, it's all in how the engine runs. The idle mixture is also influenced by the high-speed needle. Most non-pumped O.S. engines have the main needle set between 1-1/2 turns out and 2 turns out when running at full throttle on the ground. The idle needle is adjusted after that.

A basic setting procedure would be to start out with the idle mixture set to "stupid rich" and the high-speed needle about 2+ turns out from closed. Start the engine at 1/4-1/3 throttle and advance to full before removing the starter battery. Adjust the high-speed needle to just rich of peak RPM and then retard the throttle. Adjust the idle mixture as needed until you get the best idle RPM that gives you a good throttle transition.