I'm sure you'll find some. I tried the TCW3 stuff, UCL, etc. I've logged every tank of gas in all my vehicles for almost 20 years now.
Not once could I pick out statistically significant changes to mpg based on fuel additives. What was the most immediate, repeatable improvement to mpg?
Driving slower.
65 mph vs 75. Big difference, and this was in fuel efficient, aerodynamic smaller vehicles. Trucks/SUVs would be even more so.
What do I use now? RLI Bio-plus. My VW is a turbo, GDI. RLI is the only thing I found that might help valve deposits (recommended by Audi/VW owners, along with RLI oil, for deposit control - although I just run Mobil 1 and LC20)
I have 68k miles on my VW. No signs of intake valve issues. But since I don't have a control car to compare it against, I can't say that RLI did or did not do anything. Low, cheap, treat rate, so I continue to use it - just in case. 1oz per tank - gallon lasts a long, long time.
I could also never tell any difference in drive-ability, idle "smoothness" or any of the other butt-dyno claims that so many people tout. *shrug*