Originally Posted by MotoMando
My 0 to 60 mph went from 11.5 secs to 8.5 secs avg. I drive it like a banshee at the cost of MPG.
Thinking this provides some insight. Great that the 4.6 worked out so well. For what its worth, my 3.9L can maintain 75 and traffic on highways no problem. On longer grades, down shifting to 4th is required. But that is due to running 33s. On 31s, it can maintain 75 on (shallow) grades in 5th.