Help with exhaust warning lamp VW Lupo 1.0 AUC

Hello dear Forem members, I have a huge problem and am at the end with my Latin. I or my workshop have been doing the problem for a few months. Dates of my Lupo: 1.0 liter. 50 HP motor code: AUC, year6/2001, km:149000 Up to now the following parts have been renewed: Ignition coil/Zündkabel/Zündkerzen/AGR valve/Lambdasonde in front of Kat/Rosselklappe completely disassembled and cleaned. After about 350 km drive then suddenly on this “scheiss” lamp again. I am in despair. has already cost me several hundred euros. Does anyone still have any advice what could be now ??? LG Peter