Taurus idle

I have a 99 Taurus 24 valve dohc 6 cylinder. There's 90,000 miles on it. My check engine light is on. Have had the codes ran and found out that the egr valve has an insufficient flow. Replaced the egr valve and position flow sensor. The engine light is still on and still is showing egr valve insufficient flow relatively new parts, and also codes p0171 and p0174 bank 1 and bank 2 fuel too lean, and a misfire in the 5th cylinder. I have changed plugs and wires still have the #5 misfire, I have cleaned the egr valve as a local mechanic suggested, and I have taken off the mass air flow sensor and have cleaned that. Still have the same problem. The car idles at about 500 rpm and will go dead if the accelerator is not depressed regularly. I also have no brakes when the car idles at this rpm. If driving at normal speeds brakes are fine, but when I turn into my driveway and the rpm's drop, my brakes go. Help! I have been told it could be the maf sensor or O2 sensors, but some tell me that it can't be O2 sensors. I'm at a loss.