How do I know what pressure it is putting out?
This is why I have write that it is the most difficult adjust, because without bench test, there are no way to monitor the pump pressure at low, mid, and WOT on the road, pump pressure is directly connected with the timing curve.
And why need to re-adjust the pressure...... when one put a bigger plunger on the pump, the plunger/came plate counter torque is bigger on the timing system, and the timing does not move as much as with a smaller plunger, in this case, you must up the internal pressure to counter the effect, It's complicated, because the counter torque with bigger plunger is not proportional at any RPM, and also affected by the load on the accelerator.
Your factory pump pressure with a bigger plunger is ok for the idle and mid range RPM or load, but at WOT acceleration and higher RPM, that need more pressure to act the timing.
These pump part is hard to find, that take some custom made on the regulator.
For first, begin to try with factory pressure, and if you notice that the power is flat starting from 3000rpm, PM me and I will give you more trick.