I think I got about 1.5 better during freeway driving. Its all negated as soon as you stomp it to the floor though.
I do seem to get a little better mileage when I drive slightly agressive with the turbo, it likes the load.
It is noticeable compared to driving like a puss.

 

i cant give before and after but with the 408 i got exactly 12mpg towing a ~4000lb trailer at 70mph. for a 408 with a trailer that seems prety good to me. whats so nice about having FI is the truck will almost never have to shift down. it just lugs along at a low rpm(sometimes under a little boost)

 

True, the temptation is too much to resist. I feel like a crack-head when I drive my truck.

 

I'm about in the same boat as every one else, the best I ever got on the highway before the turbo was 17 and after was 21. Right now, I'm getting about 17-18 with a mix of city and hi way. if i'm just driving in the city, I get about 15. Could probably to better if I didn't want to listen to the addicting whistle

 

Thanks guys for posting up I wanted to know for my own benefit and also to prove a point in another thread. Thanks to those that posted up

 

driving you nuts wasn't it?!?!?

 

Yes I have to be right when I truely believe in something. I think this thread proved my point.