Awesome car made better with HHO system. I wouldn't bother with a VW that's not diesel, why would you? 40-50 mpg race car! How can you get any better?
The engine, of course.
HHO, deal with a reputable company that has a professional looking system and lots of experience. No do-it-yourself. If you hook it up without putting correctly into the fuse box to a connection that turns off automatically, you will blow it up if it runs all the time!