Want to buy headers or maybe supercharger for 1999 4Runner v6

I'm new to the forum, and am interested in adding some power to my old tired 4Runner. I've had it since new, and it's an SR5 model 4WD but starting to show it's age. It's got 180k+ miles, and I just replaced the radiator and injectors. Read on here about the strawberry milkshakes, and the 3rd injector had failed. Still the engine no longer gets decent mileage - maybe 15-17 mpg at best (usually 15) since we switched to alcohol in our fuel in my part of the world. I'd like to add either a turbo or supercharger. Or possibly headers? It's a daily driver, and deer hunting rig each Octoberish. But I know little about any of these options. The rig is all stock and has most always been garaged at home and work, so its got good bones and no cancer anywhere. Was reading that Toyota was no longer making superchargers? Is that true? Others say you can get one used for maybe $1500 an up. Saw a new one on fleabay yesterday that was advertised as the last one for $15,000 (no typo!). What's up w/ that??? Are they no longer easy to find? Or should I just consider headers? Money is always an object in my household, but she's never left me stranded, was paid for long ago, and I can't sell her. Bought a new '14 Tacoma TRD-OR access cab, but frankly prefer driving my old runner. Anyway, enough said, and you guys sure are a great and helpful resource! Thanks for all of your posts!
Steve