and controlling a dynamic underbalance or dynamic overbalance condition in a desired formation zone 33 so as to improve fluid communication in this zone 33 of the well in accordance with the present disclosure a downhole tool assembly 34 is lowered into the wellbore 12 in a zone of previously formed perforation tunnels 32 the tool assembly is suspended in the wellbore 12 by a carrier structure such as by a cable 36 that extends through the wellhead 22 the lower end of cable 36 is secured to a head 38 which in turn is connected to a casing collar locator 40 and a firing head 42 a downhole tool 44 in the form of an elongated hollow gun or tube has an upper end that is connected to the firing head 42 and a lower head attached to a connector 46 with a threaded end plug 48 the downhole tool assembly 34 includes an upper plug assembly 50 positioned above and in communication with the downhole tool 44 and a lower plug assembly 52 inverted with respect to and similar in construction to plug assembly 50 and positioned below and in communication with the downhole tool assembly 44 because of the similarity and construction of the upper plug assembly 50 and the lower plug assembly 52 only the description of the lower plug assembly 52 is set forth hereafter fig2 shows the downhole tool assembly 34 in an installed or unfired condition while fig3 illustrates the downhole tool assembly 34 during a fired condition fig1 6 depict the downhole tool assembly 34 as used to focus and control the effects of dynamic underbalance.