Personally, I've had good luck using Caikote. I've used it on two of my synths (my Mono/Poly and my Polysix)...
http://synthhacker.blogspot.com/2012/12/dead-keys-on-old-korg-try-caikote-44.html
Chip
Message
Re: Temperature of YOUR Polysix?
2013-12-31 by <chipaudette@yahoo.com>