Lots of people, even techs do not understand how a higher value pot (potentiometer) will raise the gain of a guitar.
This comes from not knowing how the pot works.
Your pickup is connected to one side of the pot. The other side of the pot is connected to ground. Between these two outside tabs, there is an "element." This is just a resistor and the pot's value. If you have a 250k pot, the "element" resistor is 250k. The middle tab of the pot is connected to the shaft of the pot. When you turn it, the wiper goes around the element varying the resistance.
The important part of this info is that one side of the pot is connected to ground. Even with the volume on 10, the pickup is connected to ground via a resistor/value of the pot. Some of the pickup's signal is "short circuited" to ground and lost.
So - raise the value of the pot, from say, 250k (which is 250,000 ohms) to 1 meg (which is 1,000,000 ohms) and the resistance to ground is higher - LESS of the signal is shorted to ground, MORE of the signal fights it's way down the guitar cord to the amp - the pickups become hotter, and frequency response is raised because there is much less load on the pickups. Higher pot value means less load, Less load means more gain. Easy once you understand it.
Check out the 1 meg long shaft pots for Les Pauls. Never before available (and they should have always been in the guitars) We make them - one at a time, they are cool, and only available here.