I bought a tube intake from Kurtis Cleere. It's a great deal for $75. Good quality and fits perfect. I added a K&N and took off the top of the filter box. Mine is the 3.5L.

Initial MPG results: before 13.3 MPG after 14.75 MPG

I tried to replicate the driving as much as possible. My commute is 31 miles of mixed I-95 and backroads, so I drove only that route for a few days to make sure I was not skewwing the results.

So it looks like what I've read about getting 25 more miles per tank is pretty accurate. Total mod cost was $125. Should pay for itself in about 2 months.

 

looks cool, i might end up getting one.