I have a 2003 Sonata that works as it is idle.

I have a 2003 Sonata that works as it is idle but stalls as I try to take off when I accelerate. The problems started about three years ago when the car would stall while driving it on the road. The car would bog down and run at about 5 mph and then it would turn off. I changed out the fuel pump and worked for about three months. I then changed out plugs, camshaft sensors and even the timing belt because the car would not start. After all this the car worked for a few months and began stalling and bogging down again. The occurrence of the bogging down would occur once in a while just like the previous times. This situation continued up to this moment as we speak. The hand held computers have indicated that there is a problem 171 lean fuel. I replaced the AGR valve last week and then the computer indicated the thermostat/oxygen sensor and also the sensor where the manifold cataylic converter is. The sensors on the manifold/cataylic converter looks to have a grayish to cream color to them. I did not replace them because the computer now indicated something wrong with the air flow sensor next to the air filter. I replaced the air flow sensor. The car worked for about two miles running and it started stalling and bogging again. At present the car can run at low speed and eventually take off if you accelerate at a very low speed. Once it takes off, it will run on the freeway. When you come to an intersection, the routine starts again. I am running out of patience. I'm afraid of going to a dealership and they tell me it needs all kinds of sensors. Please help.
Al Lopez Weslaco, Tx. 956-472-3361 or 956-969-2342