My understanding is that the European-spec 1.8 liter 914s (AKA the "1.8V" engine) used a pair of single-throat carbs, not dual-throats. 40 PDSIT, I think the designation was??
Makes sense. Well, if the 40 is bases on the main opening(liek the Webers) then a venturi change may help the flow like on the webers. I will be running 40 IDfs on the 1910 with 32mm Vents.