Welcome to EcoModder...
I'll second reformed's comment: get instrumentation (a ScanGauge). Driving technique is the simplest/quickest way to big savings. You can chip away at mods as you hone your skills.
As for the tornado and ethos, I'm afraid that's money out the window.
See:
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Fuel saving gadgets - a professional engineer's view
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Fuel saving gadgets - a professional engineer's view: Ethos FR