yellow engine diagnostic light on emission valve exceeded on 2004 Dodge Sprinter 2500

Van is lacking power Can't drive over 68mph Is engine in emergency mode. we have had this issue with the turbo before

2 answers
EGR valve was my problem. Poured a bottle of Cleandiesel (silver bottle) and then added some with each tank of fuel solved my problem. (too much soot)
Sorry, not enough information, Possibilities: bad transmission, Turbo, Catalityc Converter, Fuel injection system etc. refer to a Sprinter dealer for diagnostics