it may sound strange but a light pressure turbo system may provide a fuel savings. I am currently researching a LPT system for my wagon. My research has shown that a low (2-5 psi) boost turbo system will keep the transmission in lock up on hills resulting in a small improvement in FE. If I end up with the same FE and a touch better freeway performance I'll be fine with that. Having the car downshift to 3rd and even 2nd to make hills is ridiculous.