Dale Davies said

Pressure - is a value exerted equally in all directions.
Force - is a value exerted in one direction.
In a cylinder;
Force is equal to the pressure exerted on an object × the area the pressure is applied to, in our case -
Pounds per square inch × the area of the piston, or more easily referenced as the area of the bore, in square inches.
OR, pounds/square inches × square inches. NOTE, the square inches cancel eachother out, leaving pounds force.
Obviously the same pressure, in PSI, acting on a smaller piston will exert less force pushing that piston down. Conversely a larger piston with the same pressure acting on it will exert more force.
Given a given cylinder pressure, it acts equally on all surfaces of the cylinder. A larger or smaller piston has no effect on the pressure acting on it, the pressure is the same. Now this is accepting we "freeze frame" the piston motion at say TDC.
Increasing the area of the piston "can" increase the mass or weight of air drawn into the cylinder, if the stroke is the same. This "may" increase HP, but that is dependent on a number of other factors. The main one there is camshaft LCA and duration, which affect where in the RPM range the torque peak will occur.
In post #133, you stated you still do not get it, force and pressure. Obviously you are correct in that when dividing you pressure by the area instead of multiplying. Back to science class you go.

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