Did you say you had a white spring in there? I could be mistaken but I thought the two lightest springs in the HOlley spring kit were Yellow (Short) and yellow (long).
Also I looked on the package and they show values for opening and fully open based on the displacment of engine. On a 400 CI engine, with the lightest spring, you still don't open all the way until over 5000 RPM.
So a vac. sec. will never be like a mech. sec. carb in my opinion. But I run a vac. sec. in my camaro and my 48 PU and I think they work quite well so i stick with em.