In the Abhidhamma manual from Dr. Mehm Tin Mon I found on p.29/30:
7 akusala vipaka citta
8 ahetuka kusala vipaka citta
The one extra citta in the kusala vipaka cittas could be the missing link to kama guna. It is the somanassa-sahagatam santirana cittam or investigating consciousness accompanied by joy. Thus when eating tasty food we will have
– tongue-consciousness accompanied by upekkha,
— followed by receptive consciousness accompanied by upekkha,
— followed by investigating consciousness accompanied by upekkha,
—- followed by investigating consciousness accompanied by joy.
All are vipaka citta but the end result is joy (somanassa).