There's 2 different music acts under the same name Yumbo.
One is a very important Japanese lo-fi/avant-pop/experimental project of 澁谷浩次(Koji Shibuya).
Their web-page could be found here: http://red.ap.teacup.com/yumbo/
Another one Yumbo is an electronic artist from Dunedin, New Zealand, initiated in 1998, drawing influence mainly from British and German dub producers of the 1990s, as well as the jungle sound of the early to mid 90s.

Read more about Yumbo on Last.fm.