Hey Jim, cool that you got Dan's vapor tube to do well on your Hyundai!
I learned of a way to introduce a small amount of water vapor (and/or gas "cracked partially to Hydrogen") on a site I found several months ago. This is a DIY type project but easy to do IMHO.
This uses exhaust heat to heat input fluids to 300F+ degrees, then direct them to intake or a TB vac. port, or just the air intake duct. Dunno, take a look , might work for you.
Jim I hunted around in this Huge message thread to find one of the Moderator's well-drawn diagrams. There are others in various places, the thread is over 4 yrs. old, up now to pg. 200! You could do a syst. like this cheaply to generate steam vapor. I would already have one of Dan's systems myself, but my vehicles are all too old for it..
Tracy G