[Goat Blower]

Fatty might be right for once. The large turbo is fed the full exhaust stream and the smaller turbo is being fed from the exhaust after passing through the hotside of the bigger turbo with a gate just after that. So I'm guessing the gate is closed building pressure in the exhaust and spooling the little turbo which creates a ram air effect into the intake side of larger turbo and once the larger turbo starts making a predetermined amount of boost, the exhaust gate is opened which stops the smaller turbo from making boost and becoming a restriction.