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Basically as the title says, when I accelerate quickly, for example when overtaking somebody, usually from about 40 mph, I get the Restricted Performance warning light come on and reduced performance. The problem I have is it's intermittent. It first happened about 6 weeks ago during what I admit was pretty aggressive overtaking. After I stopped and turned the car off, when I went back to it an hour later it was perfectly fine again. During the next 4 weeks it drove as normal, including a couple of hundred motorway miles and 3 days in the Lake District at various speeds including some fast overtakes (on dual carriageways etc.) and at times pushing it harder than I have at any time the issue has occurred. No problems at all. So it's not happening at any specific speed or engine temperature. Then last Sunday it happened again, once again when accelerating fairly quickly from about 40 to 60, and again today. Neither of the last 2 times was particularly fast or aggressive, just what I would call a normal acceleration when overtaking. On each occasion the car has warmed up for at least 10 minutes, in fact last Sunday we'd been out for the day and drove about 60 miles at various speeds before the problem occured so I'm not pushing it from cold. I tried stopping and turning off the ignition today to see if the warning cleared straight away, but it didn't. But if I leave it for a while and go back to it, it runs perfectly fine again. Anybody have any ideas?

Thanks Peter. When I got it the DPF needed clearing, and I did a 60 mile motorway trip a couple of times and still couldn't clear it. I bought a 3-pack of STP DPF cleaner fuel additive, did another 40 mile trip and that clears it and its been fine since. On that basis it might be worth adding a can of EGR cleaner, can't do it any harm to try. That said, the fault warning light seems to kick in under hard acceleration, so I would be surprised if it was anything to do with the EGR system as I thought they only kicked in under low loads? It could be though as its only done 53k but I get the feeling a lot of it must have been short town journeys. Anyway it's going in to the dealer I bought it from in the morning so I assume they'll put a fault code reader in it and take it from there. Will update when I have more details.