This is regarding an argument I'm looking to settle with my friend, over in particular a Triumph TT600 motorcycle. When off the throttle and above 6k RPM, the engine will 'hang' at 4.5k-5k for a few seconds before dropping. He has a power commander installed and can edit the fuel mapping at will.
What I'm after is this: can an engine be 'too lean' at 0%/Closed Throttle? Is some fuel injection required to avoid pre-detonation or 'too lean' conditions? Or could I just use the power commander to remove more fuel from the 4k-6k, 0% throttle range safely?
Note: To settle the argument, references and/or a well reasoned theory will be required.