Wonder if Koch has taken a look at the turbo diesels in the '98-'99 Mercedes 300E's. He probably has, but am guessing that those TD engines are probably more expensive, less readily available and probably more complicated to work with.
Mercedes apparently added a turbo to the 300E diesels in '98 and '99 to boost power and make the sedans a bit more competitive with other euro sedan makes/models in terms of performance. The 300E TDs, engine code "OM606" (actually OM606.962 for the TD version) were apparently 24V inline-6 and came from the factory producing 175hp, 243lb/ft torque.
Pretty sure that emissions issues for the TDs caused Mercedes to stop offering the engines after the '99 model year. Next diesel mercedes offered in a sedan was apparently the bluetec diesel in the mid 2000s.
Do know that the '98-'99 300E TD sedans were/are apparently fairly popular WVO conversion candidates. Saw that biodiesel fuel supplier and conversion installer, LoveCraft had apparently done quite a few 98-99 300E TDs in the LA area.
Also saw video here and there of people tuning the '98-'99 E300 TD sedans to make a lot more power. Chip, larger turbo, and so on.
Remember a few years ago, there was this dude and his son who both owned '98 or '99 300E TDs that they'd tuned quite a bit and also converted for WVO use. One of them had put up a video on youtube, or maybe it was Google video, showing one of their TD E300s getting dyno'd; also showed the dyno results. Think torque numbers were in the 400 lb/ft range, IIRC. Will have to find that if it's out there.