That's the question of the day.

In short, you can't.

As the systems age, the theory is that the ALDA does not provide the fuel as specified by the factory setpoint and the engine is running leaner than it needs to be at most operating points. This results in a "sluggish" feeling off idle until the turbo builds some boost.

The solution is to adjust the ALDA to provide more fuel until you start to get some black smoke under certain operating condition. Then, it's set too rich.

It's a bit of an iterative process. There is effectively no way to determine the proper setpoint of the ALDA without driving the vehicle and looking for smoke.