2000 was one of the years they were known as Optibombs.
It wasn't just injectors. Some blew due to the way the cooling system worked. I can't remember which cylinder, but one was especially prown to popping because it would run too cold.
If you're really interested in the motor, I'd try and find a Merc mechanic to run the serial number to see what if anything has been done to the motor, check hours and to give it a good go over.
BTW, my feeling is that 2003 was when everything started coming together for Optis in that size range. B4 then it seemed like a **** shoot. One guy got a good running motor, the next guy got a lemon.
- Dae