Here we go... Sorry for the essay but I felt that a bit of history may help.

My 407 has 95,000 miles and to say the least has been well and truly used and abused. I purchased the car with 18,000 miles in Feb 2008. All the mileage has been created from a 100 mile round trip to work and back (All motorway mileage). For the last year the car has been shaking/misfiring when cold (but only at idle). When driven and revved the misfire seems to disappear but come back at idle if still cold. Also the revs at idle are slightly higher than normal. Then when I drive for a few minutes and the engine has begun to warm everything is running smooth. Hence why it has been ignored for so long. (No warnings lights at all)

My car went for an MOT but failed on the emissions and with a new software update from Peugeot the problem was resolved.

A month or so after this the car was doing its usual shake/misfire and I decided in my wisdom to put my foot on the accelerator to increase the revs and help warm the engine up. As the revs went up to about 1300 it dipped by about 500 and a warning of "Depolution System Faulty" came up. The car went into what the Peugeot garage called "Safety Mode" which from what I gathered limits the amount of revs you can go to? The car was booked in and it was misfiring on the second cylinder. They replaced all spark plugs and a new coil pack but said that they thought it may be a faulty injector which could have set off the spark plug/coil pack but to try this first.

When I got the car back it was fine for a few weeks but still shaking at idle as usual when the warning came up again but then disappeared. I did a 1,000 mile round trip across one weekend straight after this brief warning and everything was fine.

This has now led to the same error coming back again 5-6 weeks after the garage visit and the idle shake becoming more vigorous.

My concern is that Peugeot could just be throwing parts at the car instead of actually finding the problem. From what I've researched so far it could be broken valve guides or the rings or a software issue? Does that sound about right? If there are more alternatives then please let me know. If the injector was faulty then there would be no buzzing from the injector from what I’ve looked into. Would Peugeot be able to do checks for this and other possible problems, instead of what I fear is guess work from Peugeot?