I worked at the EPA lab during the time this testing was performed though I didn't work on this particular project. Later on I had significant dyno seat time in the 240D shown in the pics (it was chocolate brown) as it was used to run aftertreatment (often called "catalyst") testing.

Anyhow, the Comprex was an experimental system provided by (IIRC) Mercedes though they didn't make the device. As I recall the Agency was OK with this device though Mercedes decided not to produce it.

Bottom line - don't go looking for one of these. Only a few were built and fewer made it to the US. To the best of my knowledge none were US-spec and therefore were either sent back to Germany or destroyed at Mercedes' discretion.

It was an interesting job.

Dan