I don't believe that there was a change of cam for the 2.6 engine, and imagine it uses a similar cam (perhaps the same) to that in the original 3.0, before the change of cam design.
It makes 167 bhp, against the 3.0's 187bhp (both in Europe), which means a higher bhp/litre for the 2.6 (64 vs 62), so I'd suggest no other M103's cam would give more power.
If you want more power, go with an aftermarket cam, but be warned that you will lose low-down torque (something I would never be willing to change about my MB).
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black