I would see if you can't find the Pro Design intake manifold built just for VF3's. This whole piece that has been giving you Hell is the 'stuffer block' for the VF3 reed cage. Stuffer blocks are used to reduce the volume of the reed cage, so that there is not a sudden change in size of the intake tract between the carburetor and the crankcase. You can actually run the engine without this stuffer block even being used; throttle response and tunability will suffer a bit, but it will run until you can find a permanent solution to the problem.