Oil Pump problems of the 2004 Jeep Grand Cherokee

At 17,000 miles my 2004 Jeep Grand Cherokee laredo freedom v-8 4. 7 ho engine developed a rough idle. The dealer cleaned out the fuel injector and the problem did not go away. 2nd time they put it on the computer and couldn't find anything wrong. The #2 piston popped in and out so the mechanics agreed something was wrong and recommended a new engine; but the manager wouldn't do anything. They agree the vehicle runs rough and notice the vehicles on the lot run smooth. They suggested I change the spark plugs which cost me over $200. 00 and that did not help. The dealer did change the oil pump and put in 8 new lifters. This still did not take care of the problem. The district manager stated all the Jeeps run that way. He and the manager above him both state they will do nothing for me and they are closing the book. I have talked to several Jeep owners with the same vehicle. Some have a rough idle and some run very smooth. Other reliable people have told me the problem is the computer. When I told the service manager he said to put the engine in low and it will jump the computer into shape. The idle is getting worse and has affected my gas mileage. I am still under warranty and am getting no where with Jeep or Chrysler. I now have over 31,000 miles and am nearing the end of my warranty. I don't know what will happen if the computer just dies. I imagine the engine will stop on the road and possibly cause an accident. If you could look into this I would appreciate it. I just want Chrysler to stand by their product and come up with a solution so I can be assured of a safe vehicle. Another thing is they never give me paperwork after they've had my car for a few days to check things out. They always tell me it's still open and when everything is finished they'll give me paperwork.