A process for stimulating a formation is disclosed wherein a diverting fluid is used to divert an acid treatment package from a high permeability or damaged portion of a formation to a low permeability or undamaged portion of a formation. The first transistor has the other end connected to power supply. An expansible chamber device is disposed within the die cavity and changes volume in response to changes in fluid pressure within the expansible chamber device, which may be regulated by a means for controlling the volume of the expansible chamber device.