No..accumulator tanks only reduce pump cycling. They have to be set couple of psi less than pump discharge otherwise pump can not start or refill tank.
In order to increase line pressure & flow you have to have a higher discharge pressure & flow rated pump.
Check out reviews of the 'Extreme Series' pumps.......several have had problems.
What model # of Shurflo Pump do you have?
I have the 2088 model......2.8 gpm at 45#
You can increase the discharge pressure via an adjustment screw on end of pump head.....clockwise to increase BUT only in small increments.