The specs to look at for helping with distance have always been weight and length. Flex in some cases, but only when the shaft your playing is really misfit with regards to flex. You want to play the lightest, longest club you can control. I don’t know the weight of the shaft you are playing, so suggesting lighter might not be relevant. Assuming the shaft you have is somewhere in the 60-70 gram range, I would move to something in the 50 -58 gram range. Obviously length needs to fit you and if your comfortable with the length of your driver, I would not lengthen it for the sake of maybe getting a few more yards, but possibly sacrificing accuracy. Still, maybe something to experiment with. Difficult to make specific shaft recommendations not knowing your trajectory needs, or the price range your looking at. There are several good shafts with 50+ gram options to consider. When looking at options, focus on the weight of the shaft in the flex that fits you and the trajectory profile that you want.