Yeap

 

please correct me if i am wrong:running lean will let spool better but will not let run more boost.

 

We're talking about different points in the power band here. Theoretically, running a leaner mixture out of boost will allow the engine to act more like a high performance Naturally aspirated engine. Running a lean mixture at peak torque and/or at peak cylinder pressure points is incredibly dangerous and very different.

If a car is triggering a fuel cut at X boost pressure at a certain Air Fuel Ratio, leaning out the mixture in an effort to run Y boost pressures is something we've seen tuners do with the direct injection models. In this regard running leaner and avoiding fuel cut would allow for more boost to be sustained. I refer to it as Russian Roulette tuning, only with a pedal instead of a trigger and an engine instead of a bullet. The sad part is that this method doesn't actually make more power, it just breaks things.