With the EP Turpasauna in 1990 the language changed into Finnish and the music became more complicated. Soon a fourth member joined the band, keyboardist Tommi Kärkkäinen, since more musicians were needed to carry out the varied ideas of the artists. In 1992 on the single Daavidin fuzz / Paratiisin sahakielet the crew had changed again: Jussi Hyyrynen had switched to the guitar and Janne Mannonen had been hired to be the new drummer. The current form of YUP dates back to 1994 when the keyboardist was changed to Petri Tiainen after the album Toppatakkeja ja Toledon terästä. Tommi Kärkkäinen begun to compose classical music.
The album Outo elämä from 1998 is widely considered the breakthrough of YUP. After that the music has become somewhat lighter and easier to approach, which has upset some hard-core fans. Their compilation releases ironically reflect, the album being called Helppoa kuunneltavaa 2004 ("Easy Listening"), accompanied by the DVD Helppoa katseltavaa ("Easy Watching") and the songbook Helppoa soiteltavaa ("Easy Playing").
The latest release Keppijumppaa from 2005 took a step back into a more raw and complex sound.