What's so odd about not wanting to burn unnecessary gas when it's not giving you any fun? Performance driving is performance driving, whether you want gees in the turns or high mpg during a depressing commute (if you can't pass them, at least get stellar mileage while you're stuck in that line of cars).
I came here when I was in my 05 Legacy GT. I wrenched that thing from 22ish into the 30s, never quite getting a 35 mpg tank. And I had a blast doing it. Man, I loved that car:
I'd say don't buy different wheels and tires yet, buy a ScanGauge or UltraGauge instead. The only thing that's going to get good mileage out of that car is
you. If you want to buy a thing that will simply hand you good mileage, get a Prius. But you're a driver, so you've got to do the performance driving yourself. And you can't do that without seeing real numbers and understanding how your driving affects them.
Learn to P&G well, you'd be amazed at how much of your commute can be done in neutral. Get good at bump starting- you'll be even more amazed at the parts of your commute that you don't even need the engine running for.
Once you learn the car, and you can't do that without one of those gauges, then you can try modding the hardware. And you won't have to ask advice, because the real question will be "with my driving style on this commute in this car, what will help my numbers?" and only you will be able to answer that. But don't worry, you
will be able to answer it.