So, here's my review of the Dual-Stage Boost Controller:
Rubbish. Mine could not control boost in either stage, at any time, in any configuration. I bought a Chinese one, of course, but referred to TurboSmart for installation and troubleshooting, since it's a knockoff of their design. Installation was easy, but the unit was cheap and eventually, the knobs for adjustment stuck in their respective positions. I don't recommend it.
Just go with a Hallman in-cab controller or something of the like.