Since you are not relying on power from the IVR for oil pressure and temp, we cannot see if those gauges are also experiencing malfunctions. If they were, I would lean towards the IVR. I would say that your problem is either the ground strap, the IVR or the sending unit. If you are so lucky as to have the gauge read empty while you are in your driveway some time, crawl under the back of your car and give the gas tank a few good smacks. If it is a bad/sticking sending unit, this may well temporarily jar it back into life. Also, if the gauge is reading empty, try using a jumper wire with alligator clips and grounding out the tank to a known good ground. If the gauge works now, the problem is likely a bad ground strap. If these two tests do not work for you, then I would certainly consider the new IVR route.
