Headers
The headers LOOK small, but think about it. The exhaust in a Turbo Buick is running under substantial pressure, maybe as much as 30 psig. That compares to 1 or 2 psig in a normally aspirated engine. It means that the volume of exhaust gas is much smaller, even allowing for boosted intake flow. The smaller pipes keep velocity up, and pressure up, to drive the turbo. IF you put in bigger headers, you will lose low rpm boost. The guys with the really fast cars can tell you when headers are needed- my (almost stock) Buick never leaves the street, but I thought I would throw in some "theory".