Hi Daz, You say that the lambda is between 97mv and 800mv but at what speed is it switching? The Peugeots are hyper critical on lambda sensing and if the sensor is not switching hi-lo at atleast 1Hz ie; Once per second, it can cause the sort of problem you are having. Scope the lambda at the engine speed that the problem occurs and it should have a nice switching rise and fall pattern with no glitches or flat areas appearing. If it does not switch at 1Hz then suspect the Lambda. HTH mate, Gunner.