What's the difference between the JGC 5.9 Limited and the standard Magnum 360? I noticed looking at 5.9 Ltd specs today that it makes 10 more hp, and more importantly, 20 lb-ft more torque at 400 less RPM than the Magnum. Is this stuff I could do to my own Magnum?

 

"The Grand Cherokee 5.9 Limited combines the sophisticated performance of a more powerful 5.9-liter V-8 engine with additional luxury, smooth handling and legendary Jeep capability. Grand Cherokee 5.9 Limited is the fastest, most powerful Jeep vehicle ever, with a 0-60 time of 7.3 seconds.
The 5.9-liter V-8 engine produces 245 horsepower at 4,000 rpm and 335 foot-pounds of torque at just 2,800 rpm. Also new on the 5.9 Limited is the 46 RE transmission, high strength output shaft on the existing 249 transfer case, electric engine cooling fan and high output 150 amp alternator.
In addition, Grand Cherokee 5.9 Limited features a new free-flowing exhaust system that reduces back pressure by nearly 25 percent and contributes to the high-performance capabilities of the vehicle. A three inch chrome-plated exhaust tip finishes off the low-restriction muffler that provides a throaty "performance" sound."

Those are some of the reasons why. They also have a special computer program that requires the use of 91 octane gasoline or better.