Posting the resolution. I started over and retested everything again. Seems I had multiple bad senders, even one that was brand new. Purchased another new unit and all is working good.
I have pulled the cluster and done a ton of testing. Gauge out of the cluster, it works fine. Pegs at full ground and goes to various levels with different resistors.
Sensor wire does not go directly to the cluster, it must split off to a module somewhere as it also feeds the red warning...
Thank you for the replies!
I verified earth straps are in place. I added additional earthing to the block for testing.
I used a 10 ohm resistor between the wire and an earth, multiple places on the body and the engine, even back to the battery. No movement of the needle. I tried other...
I was having an issue where the oil pressure would randomly drop to zero then come right back to normal. I replace the sending unit and had the same issue. Several months later the gauge stops reading any pressure. I confirmed oil pressure with a manual gauge. I again replaced the oil...
I drain the oil using the drain plug at the bottom of the reservoir, I then remove the housing that the drain plug goes into (4, 10mm nuts). There is a filter inside of this housing.