Good one! Nice find. Guess the nose knows Eh?

 

This is a total shot in the dark... but if you're like me when I did the injector upgrade, you're just putting your foot into it too much.

Upgrading my injectors improved acceleration so that I didn't need to press on the gas as much, but I was used to my old driving habits and would waste gas by accelerating faster than I needed to.

If you did all of that tune up work, your engine should be running more efficiently, and maybe you really are just being too heavy on the throttle whereas before it actually needed a heavy foot to get moving.

Since I adjusted my driving habits, my MPG has returned to normal.

This is a completely wild guess so definitely look at everyone else's advice first, but it wouldn't hurt to at least consider this.

 

Good Point, Operator Error.

 

Just saw that^. Nope, still no source or hairpins. (going down the hill today though)

I was thinking the same thing about driving habits. That's why I asked in post #4, "what kind of driving do you do". On a tank when a long trip is the 7 miles to Hioucchi, 13 plus/minus...happens, but on the freeway I've seen near 20.

Low vacuum=low mileage. My old thing has about 12 inches Cruzen at 60.

 

Just wanted to update everyone. Had a day off yesterday and went out and bought a new MAP sensor from O'riellys ($59.99) life time warrenty) and took all of about 5 min to install. I instantly noticed a difference when I started it up. It even sounded better. It drives smoother so now I am filling it up today and going to see if it helped improve the MPG. Also, side note, I traced down the fuel smell problem and found out every bolt holding down my valve cover was loose.... really loose, so that got fixed too.

 

Gas should not be coming from the valve cover. Did you check the fuel rail/injectors for leaks? (which are right next to the valve cover)