The connection to manifold to sense Manifold Absolute Pressure (MAP) is to provide enrichment with increasing manifold pressure under load. As manifold pressure increases, control pressure decreases. If there is a leak to atmosphere in that line, or in the pressure chamber of the WUR, the mixture will be driven in the rich direction (particularly at idle).

Re: Control pressure at 20deg C.

Last three digits of Bosch # on WUR:
010 and 057 - 1.0-1.5 bar
103 - 1.0-1.4bar

If you have determined that the engine is stalling due to leanness, use the low end of the range. And contrariwise for richness.