Since I posted this topic, I've gathered more information that may help:
None of the global settings changed anything
Tried using Aux Input, no difference
Tried using a Gain block, made a slight difference.
Looper block is very quiet, which leads me to believe that the signal is too quiet before the chain and amplified at the end.
Tested this by setting pickup volume to the max, which worked, but the loop was still quieter than I was hoping.
The output impedance of my pickup is 800 ohms, compared to Pod Go's input impedance of "1 Meg Ohm."
At this point I might just go in for a preamp and see what happens.