I installed a supercharger on my 2.3-16. This engine is injected but some of the symptoms might be similar. First, does the engine run fine without the turbocharger pipe attached? Second, is the fuel bowl vent port enclosed in the intake duct? I am not familiar with your specific carb, but my DCOE Weber has a port next to the venturi that vents the fuel bowl. This must receive the same pressure as the venturi or pressure across the jets will be negative and no fuel will flow.
190SL, 230SL 5-speed, 95 E320 Wagon, 01 E320 Wagon, MGB, Boxster 'S', 190SL "Barn Find"