The 98 and 99 have the OM606 same family as the last generation 124s. In the 124 and the 96/97 210s it is N/A. They added the turbo for 98 and 99.

The 210 606 still has a mechanical injection pump but the computer gets between your foot and the rack.

Due to all the computer controls not sure how much tuning you can do.

However it has plenty of punch (for a Diesel) when properly sorted due to the turbo.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech