Sounds and looks correct
Ive never used a reducer, is it touching the gauge housing? Is it suppose to be insulated?
I see you put a new decal on the gauge, could the sticker be impeeding the needle? Could the bezel be hitting the needle?
The ground wire comming off the sender flange, where dose it ground? It the connection clean and tight on the other end
If you turn on the truck and remove that sender flange ground wire quickly the gauge needle should jump to full
Could just be a bad gauge
