Hi, my first guess would be a 1992 frame. That would match the cable routing and the remaining decals, and the oval headtube badge. Difficult to know which model though, although I would guess lower end as it doesn't appear to have the taper at the bottom of the seat tube that the mid-range models had or the bulge that the prestige tubed Explosif had.
All Konas should have a S/N, if that is a respray then it might have filled in the number on the frame. I would expect that to be something in the format of F2XXXXXX (or sometimes A2, T2 or H2) where the first letter indicates where the frame was made and the second is the year, third and fourth are the month. The S/N is typically under the BB shell. There are often other numbers stamped under there, no idea what they mean though, so that might be what you are seeing with the yf007.