I havn't tried it, but the tip that ran by me (likely Here somewhere) about kosher salt and everclear, (pack the bowl, fill it with everclear, let it sit overnight and dump and wipe out) ..
seems ideal. if i have an old estate pipe i'll try it.
'sour' pipe is either overly smoked and not cleaned ..
or the wrong (or way too moist) tobacco..
If you smoke aromatics you're more at risk of a sour pipe, especially drugstore aromatics..
Get it clean, let it rest a few days, try a different blend with less casing..
putting things IN to hide a foul taste doesn't work.