I've been lurking around here for many months and finally decided to register and throw in my .02 worth when I feel it will help. Three months ago I purchased an 04 Lariat 250 SD that was built in 11/03. It was a private sale with about 18000 miles on it. The owner was a real cynic about these trucks but he had maintained it quite nicely. It has never seen a dealer so it has the original quiet idle and there wasn't a tweak on it so it hasn't been too abused. The guy was in his 50's so I doubt it was abused at all. After about a month of driving it and getting about 14.8mpg, hand calculated, all around, I did an oil change. The previous owner had always used Rotella 10w-30 and he had Blackstone reports showing that, so I used the same as he gave me an extra 5 gallon pail he had out of his stack he bought awhile ago. While I was changing the oil I decided to check and see if it had the throttle valve plate that is mentioned every once in a while around here. It did, so I removed it. Within 2 weeks my mileage increased from the aforementioned 14.8 to a solid 17.08 and really hasn't wavered since. The other benefit I noticed is that the tranny shifts alot smoother with this plate gone. On a clear road I'll average 75 to 90 and around town it's 0 to 50.
I still can't believe that the throttle valve was choking this thing by about 14%.
Just thought I'd share.
Regards,
Harry