Got a good deal on this vehicle, but the intrument panel had a DIC that fuzzed out, and the fuel gauge was erratic. I replaced the IP and it fixed the DIC, but the fuel gauge was not better. When I've had that problem in the past it'* been the sender unit on the pump, so I replaced the pump....still no luck. The gauge constantly moves about---when you start it, it immediately goes to full no matter what amount is in the tank, then slowly begins to decrease, before moving back to full etc.... I've noticed that it will never go lower than the actual amount in the tank...so we can tell what amount is in the tank to watch for where it "bottoms" out. Now that we've replaced the IP, and the FP....what is left that could be causing this issue?

Check for the ground and connections.

X2 on grounds. Also look for any broken/loose wires, and corrosion in the plug on the fuel tank.

While replacing the Fuel Pump I did not notice a corrosion problem with the connections. The connections are pretty secure in the fuel pump access area in the trunk. It appears from my Google research this is a common problem....but lacking greatly in remedies.

Did you check the connections at the IPC? Maybe theres a loose wire there, or a pin in the connector that is bent, or not making good contact?

ive had to cut out the connector, solder, and heat shrink the wires that go to the fuel sending unit on a few