I have a 1988 BMW 325IX. The miles per gallon gauge located at the bottom of the gauge cluster has become inoperable. My go to shop indicates that it might be a defective main circuit board but can not say for sure. Another shop thought that it might be in the wiring that has something to do with the oxygen sensor. Anyone out there have any experience with this kind of problem. Looking for sound direction on having this repaired. The local bmw dealer tells me that this part was not available for my car, and that it had to be removed, repaired, and reinstalled. Any and all assistance in getting this problem alleviated will be most appreciated. Thank you in advance.