Obviously, weight reduction is most important in stop/start situations. I don't think it should be dismissed out of hand though as it's really very easy and completely free to pull out bits that are not required. If you only need two seats and don't care about noise, you can definitely remove the rear bench seat, seat belts and carpets in an afternoon for a saving of at least 50kg and for free. If you don't need the rear seats, then you can often sell the front and rear seats for enough to buy a couple of lightweight bucket seats that will normally (with the carpets and rear seat) save you 100kg.
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