MPG Increace

Not to be a stickler, but not having a hood is not helping you at all, for a lot of reasons.

If you aren't willing to change the engine, have you thought about swapping to an overdrive of some kind?

It takes a little patience and setup, but once it's done, you can see a vast improvement in MPG just by having another gear to put it into, especially on a 20 mile commute.

The A833 O/D might hate you on the 3.09 first gear, but another inexpensive option that requires a little modding in the trans tunnel as well, is an A500 automatic. Those can be used with or without full lockup and aren't as big as the A518. They bolt right up and you can set up electronic overdrive engage to happen progressively and have a bypass switch for manual control, as well as separate or combined manual control over the lockup converter, which can help immensely.

Another option would be to look into a Dynamic converter. They have better stator and impeller pitch ratios that allow performance stalls without a lot of slipping under cruise. They also make performance stall ratios for lockups, if you decide to go with an overdrive.

Rob is right, a fan and small tinkering is not going to get you any more improvement on fuel economy than monitoring your throttle position/ foot/ behavior, without your will to start changing significant parts.

The truth is, you can have a high performance car and get good fuel economy, but unless you start opening up the idea to an overdrive or fuel injection (both, ideally), you won't come near good fuel economy and keep your HP/TQ where it is (or better).

One thing you can do that is practically free is to monitor your driving. There have been several universities that have recorded mood/ circumstance on driving MPG and they have found that the driver has more of an impact on MPG than anything you can do to a car. Top Gear (UK) did a test on a BMW M3 against a Toyota Prius, around their track on MPG/ fuel consumption, while still attempting a reasonable and relative E.T. The Beamer SPANKED the Prius, and I'm not surprised, considering how hard they were driving the Prius.

Get a vacuum gauge and keep as much vacuum as you can, with your right foot. It's dirty, cheap, easy and will save you more gas than anything else, outside of some other mods that I think would help your HP and fuel economy (overdrive and injection).