Twin Sequential Turbos= Use two low tech turbos with different A/R's to reduce turbo lag: One works good down low, and the other one up top. Low tech is usually cheaper and "Twin Turbo" sounds really cool. ---See RX7, Supra, 300ZX.
Once you understand that, you might have a chance at seeing why a VATN turbo is better than twin low-tech turbos.
VATN Turbo= One turbo that acts like two. Vanes close down at low exhaust gas volume (low RPM's) to spool it up (like Porsche). Once the volume of the exhuast gases go up, the vanes open to allow the gases to flow by, still spinning the turbine.
---See Mercedes, Mopar, Audi, BMW
Corkey Bell has a neat book out. Sounds like someone needs a new "engine builder" and needs to realize there might be a better way of doing things.
