yeah, i'm not sure if it would work.
what I wanted to do, was take 2 of the same model turbos from a junkyard, and build a twin turbine engine, in a mutual relationship. instead of the combustion chamber being in between intake 1 and exhaust 1 (like normal, intake goes to combution, spins exhaust to spin intake, it would be like this
intake 1 to exhaust 2 exhaust 2 spins intake 2, which goes to exhaust 1.
so the power produced by intake one would spin up the other turbine, and the power produced by intake 2 would spin up the 1st turbine. starting it should only take a leaf blower into one intake, since once the combustion starts it would be self supporting. Doubt it would have good respons, but it would look kick ass.
I see how your idea works, but it can only spool up so high before the vacuum stops doing anything. it would require some sort of flywheel for it to keep spinning, so spooling it up in the first place to a useable level would be difficult.