Rough Start/Idle problem! Some insight please!

[uefear]

When this problem first started happening I found a elbow that had deteriorated in my vacuum line. It was causing my truck to run terrible, causing my check engine light to come on, and destroying my gas mileage. I replaced the elbow and the check engine light went away for 30 miles or so then it came back on. I ended up replacing my DPFE sensor or whatever its called ($70 bucks from the Ford dealership). That made the check engine light go away but since then I feel like the truck still runs bad. Even now my check engine light is off and my gas mileage is horrible even though I have not changed my driving practices; I am seeing about 180 miles to a full tank (about 17 gallons). That is horrible compared to what I was getting before (about 220 miles to a tank) this started happening. I did a seafoam and sparkplug/wire replacement recently. Besides that I have not made any other repairs recently. My air filter is clean so its not that. I am not much of a mechanic, but what are the possibilities of this being the fuel filter? That was the next thing I had in mind to change. Any ideas? Thanks

 

[98formulaLS1]

Just in case the computer has learned that your have replaced the vaccuum tube and sensor, you should reset the computer. I'm not 100% sure how it's done with these cars, but disconnect the battery, then touch the two battery cables together to discharge all remain capacitance thats left in the electrical system. Leave them connected for about 5-10 minutes, then reconnect. You computer will be required to relearn your new driving characteristics.