I have found that when replying here to help some one, is that with out the engine, plane, tank or what ever the issue is, right here in front of you, All that can be done is just give some fixes that are common happening in the areas the problem lie. I too have planes that the tank set up is higher than what would be best, but run fine through out the whole tank. An engine that has a good venturie size will pull fuel better than one that is sized differently. If set to restrict the push of gravity on the fuel entering the carb, then also allow good vacuum to pull the fuel as the level goes down, then it will not be a problem. I also have engines that will pull fuel fine & on another engine of the exact same , that wont. Mid range on one, perfect, on the other, rotten. At some point, the remedys given by the replys should be enough to get the problem solved. It also helps the newbies gain valuable info & insite as to how these things work, & how to self diagnose there problems with the new info they learn.