It is strange they don`t know what is wrong with your motor,I take it has been on a computer for a look at faults stored etc,it may be the case it has to go onto the correct Peugeot Diagbox computer for a look at your particulate filter in your exhaust,if it is clogged and what percentage of clogging is present, also it will determine if you need topped up with Eolys for injection into your fuel system,if this is the case then it must go onto the correct computer to reset your additive levels and may force a regeneration of your exhaust system to clear your filter. Good luck.
cdc
July 2014