Gasoline Engine problems of the 2004 Jeep Grand Cherokee

I have a 2004 Jeep Grand Cherokee laredo, 4. 0 liter, SUV. Since approximately August of this year, the engine has misfired eleven (11) times. Each time there is a misfire, there is an immediate power loss, and loss of speed, almost like an emergency braking situation. One event, on 8/15/05, when traveling on I-66 near fairfax, va two cylinders, nos. 1 and 4 misfired at the same time. The result was an immediate loss of power during acceleration and loss of speed from approximately 65 mph (rate of traffic at 3 pm rush hour) to approximately 25-30 mph within 50 yards. This incident nearly caused a serious accident, because other vehicles had to brake and swerve to avoid colliding with mine. There was no where to pull over to the side of the road, and luckily I was able to maintain control and continue at a slower rate of speed, until I could move to the right and stop in the emergency lane. After turning the engine off, the vehicle will run normally when restarted. As previously stated, it has misfired 11 times, and by stopping the engine, then restarting it, normal operating can resume. Chrysler corporation has been unable to repair the defect, after having taken it to the shop on nine or ten different occasions. They have replaced the spark plugs, tested the engine for carbon deposit build-up on the valve stems, and replaced the crankshaft sensor that the computer uses to fire the engine. Now, the manufacturer has said it may be the computer module, it may be the coil pack, or the engine may need to be disassembled to see if there is any carbon build-up on the valve stems. This condition makes the vehicle unsafe to operate, not knowing when it will happen again, and if it will cause a serious accident to occur. Maybe NHTSA can light a fire under their creative minds to come up with a positive solution. I have 63,000 miles on the vehicle, and the whole series of incidents began when there was approximately 49,000 miles on it.