Truck starts and idles fine. Drive it down the road and when it warms up it starts loosing power like lack of fuel. I can punch it and it takes right off. As rpms go down ( cruise speed) it looses power, sometimes sputter and acts like it chokes. Took to mechanic and he said it needs an 02 sensor, map sensor , egr , and gasket under carboratour. All that has been done and it still does it. I also changed the fuel filter, plugs, plug wires for good measure. It doesn't do it all the time but lately it has become frequent and expensive. Any suggestions? I can stop at lights and it idles smooth.