As you know, you should match the ohmage on gauge to sender (30 or 90) If you did that you don't need the thingamajig. Whatever that is. Pot? The number one cause of problems is the ground. Assuming you have a matched ohmage system, ALL grounds must be checked. Think of what it takes to get the sender ground to the gauge. Sender to frame, frame to body, body/dash metal to gauge, engine to body, battery to engine. Bunch of good, clean, metal to metal grounds. You can run a temorary test wire directly from sender to gauge and a convienent ground just to be sure it works. This can be done with sender and gauge on the bench if you want.
