Have you tried soaking the tube, cap and oring in lemon juice? I don't remember if that was suggested or not but that has worked for me for getting old flavors out of attys and cartos.
Yup i tried
PGA
LEMON juice
iso alcohol
420 cleaner (usually works insanely)
vinegar
soap
Boil
I still have it(tube,cap and oring) sitting in vinegar from the other day then im gonna let it sit in water for a day . It really leached into the rubber . Right now the reo is all good again well accept im using a thinner 1/16 tube i had laying around and no oring but i put in a new bottle .I also replaced the insulation on the firing pin which also smelled ad put a new bottle and newly drilled cap . Iv havent used it yet though iv just been using a carto on it since yesterday and my Provari .