1996 Jeep Grand Cherokee

My wife's 1996 Grand Cherokee has 150,000 miles on it and has the 5.2 liter engine. The check engine light stays on and the only code has been 0132 for the O2 sensor. We've replaced the sensors, replaced the fuel pump assembly (as the secondary problem listed). We also put a new muffler on (it needed one anyway) and still no solution. The vehicle runs ok when first started and after being driven approximately 25 to 30 miles on the highway, begins to shudder and act like it wants to stall at redlights. Please give me some advice on what to do to make this vehicle run right, my wife works in a different town thatn I do and before I finished the work done so far, she had me drive her to work and pick her up, which requires me to take time off from work as well as drive over 100 miles per day.