That's for a m104.991 engine which is out of the SL320 (R129). The E320 has a m104.992.
I don't know if there are a lot of differences between the two. Power is listed as higher for the SL320 version 231PS vs 220PS. I think this is because the compression ratio is higher for the 991 vs 992. 10 vs 9.2 respectively.
I read in an issue of The Star that an owner swapped the intake manifold in his wagon for one out of an R129 for more power. I am skeptical that it would do much, but that's just my opinion.