Welcome to Ecomodder.
There are more than a few of us driving S10s on here. The "sluggish" 2.2L you describe is the ideal S10 engine for efficiency, and bonus points if you have a manual trans.
Have you checked out the two things pinned to the top of every Ecomodder.com page, the "65+ Efficiency Mods" and "100+ Hypermiling Tips"? If you adjust your tire pressures, drive for MPG, and a few other basic cheap tips, you should get great mileage out of your truck.
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