We had this on a 2002 2.8 diesel motor home.
Check the connections on the throttle loom. Its fly by wire and when they convert to RHD they add a plug in wiring extension - its a 4 cable brown plug under the passenger dash by nearside wheelarch - the plug or wires to it can get a bit corroded and gives an intermittent fault - in our case when we went downhill over a bump in the road !!!!
'Repairs' cost me £300 at the main dealer ( waste of time ) and was finally located by a back street garage. Total time to fix about 10 minutes. ... and prior to that 6 months trying to get sense out of Peugeot and various dealers who washed their hands of the problem.
Ross
December 2011