Update:
Fuse 4 is the in tank fuel pump
Fuse 6 is the main fuel pump
When I apply 12v to fuse 4, I can hear a pump running loud and clear, sounds like the main pump. However fuse 6 has 12v even while the car is off.
I applied 12v directly to the in tank pump, and it sounded like someone sucking liquid through a straw, I couldn't hear a pump at all. I tested its connector, it was getting about 10v, I used a wire and connected this to the positive side of the pump, and it didn't make any sound.
I pulled one fuse, then the other, and had both out of the car at the same time, and it still ran fine 🤔
I'm guessing the in tank pump is on its way out, judging by the sound it makes with 12v applied to it, but why does my car still run with fuse 4 and 6 removed, and why is the pump only getting 10v?