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=DEBMW 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