After changing the plugs the 4.7 runs completely different. It must have been pretty bad off with those old plugs. Not only does it idle better but has better throttle response and acceleration. It honestly feels like a different engine. Since I've had it, it has always felt a tad sluggish but not anymore. I would suggest to anyone with near 40k or more miles on the 4.7 to go ahead and switch out the plugs.