1989 Ford F-150 F-150 Lariat

You may be right about one of them being a selector but I am having trouble with the rear pump. Normally I can resolve these problems with a little research but the pumps do not both work only the rear pump was working. When I would change over to the middle tank it doesn't seem to work all the time. So I've reallied on the rear tank and basically ignored the middle tank. But now I thought the pump went out without checking pressure or any diagnosis that's the direction I went and replaced it with a used pump due to the cost of the original pump being over $100.00. It runs great but does not seem to have a quick pickup and stalls on acceleration briefly. Not real bad but am considering changing it all out putting one high pressure pump maybe two and still running the two tanks but with a different selector. That selector is just to expensive. So I would like to simplify the system if possible.