[Xist]

I tried to find more information on this method.

3,000 miles before code: https://priuschat.com/threads/acid-b....166554/page-3
12,800 miles before code: https://www.tacomaworld.com/threads/...d-wash.241619/
18 months and no code: (All Years) Catalytic Converter Citric Acid Bath P0420 - Subaru Forester Owners Forum
Almost 30,000 miles without a code: P0420 / P0430 and a "Hail Mary Pass" (the "cat washing" thread) - Page 12 - Toyota Tundra Forums : Tundra Solutions Forum
BamZipPow ran it through the dishwasher and has not had a code for 41,000 miles: http://ecomodder.com/forum/showthrea...-do-23483.html
480 miles and disappered: https://www.bobistheoilguy.com/forum...topics/3391904
Tried a few things, without clear results: https://forum.ih8mud.com/threads/cat....833570/page-2
Attempted, but did not report back: (All Years) P0420 Catalytic Citric Acid Bath (How To) - Subaru Forester Owners Forum

Who knows how accurate any of this is, but there is indication that 50% of people who try this see clear benefits, but unfortunately, it seems like hardly anyone followed the directions perfectly.