[dsm-onster]

Don't cover the hole. That is supposed to be there. ALL ball and spring MBCs have/need this hole to control boost. Otherwise, once the spring/ball valve vibrates a few seconds, the boost in the line ater the valve (wastegate actuator) will equal the pressure before the valve (manifold presure). If the pressures are the same, then there is no boost control and you're running at wastegate pressure/stock boost at best.

Making the hole large curbs boost spike (not creep) when you turn in the MBC a bit tighter. A small hole causes the boost response to go up, but at the cost of some spike.