about fifteen years ago i did an experiment at home where i soaked 1994 5.9 v8 pistons for several weeks to see which liquid would remove the carbon deposits the fastest

LiquiMoly Ventril Sauber
did better than Chevron Techron, Seafoam or Chrysler ATF+2

i later learned that in German
"Ventril Sauber" means "valve cleaner"

http://www.liqui-moly.de/liquimoly/produktdb.nsf/id/en_1014.html?Opendocument&land=DE

BMW and VW dealerships stock this product

since that time Chevron has changed the formulation of Techron and now calls it Techron Plus

with the new video borescopes costing less than $200 i guess one could do home experiments to see which fuel additive best cleans off deposits on intake valves

i have wondered what a couple weeks of running E85 would do to intake valve deposits