97 f-250 power stroke

I hope everybody is still alive and well since the last time i dropped in, I have a question or two to ask.
first off, i recently purchased a brand spankin new (for me) 97 f-250 heavy duty 4x4 crew cab short box power stroke diesel with 120,000 miles on it, I new the owner and it was his wifes truck, she drove it back and forth to work everyday, it was serviced every 3,000 miles. what sort of engine life should i expect out of the engine & transmission(e4od) it also has 4.10 gears.
I lifted it 4" and put 315/75/16 bfg all terrain tires on it.

my fuel mileage went WAY DOWN, im getting about 11 mpg around town, and not much better on the highway.
I also tow a 29ft tt weighing wet at around 10,000 lbs.
is anyone running the banks kit? or ats? I would at least like to change the air cleaner assembly, it looks like it leaks, does any one have any suggestions? thanks for any help given.

97 f-250 power stroke

Try going to: www.ftw.truckmoxie.com
Go to "Forums" then scroll down to "Performance Forums" then down to diesel. If you want to ask questions there, you will need to sign up as a member. If you don't, you can still view others questions and will prob find most of your answers in past post. It is a geat site for Ford truck owners.