Just wondering whether anyone has experienced this and has any suggestions: 56plate TD4 with 56k miles, recently acquired. I carried out a full service; oil change / all filters including fuel and crankcase breather / and have also installed an EGR blanking mod and a diesel tuning box. I initially noticed that it was pinking / harsh sounding knock pulling from low revs which disappeared on wider throttle opening / higher revs. This was before service but after fitting tuning box. It has also now started running rough at low rpm / low throttle with quite harsh pinking / diesel knock when pulling. Again, as soon as revs rise or increase throttle opening it goes. Starts well, performance excellent apart from initial acceleration, no evidence of smoke from exhaust. I have tried disconnecting tuning box; maf sensor - makes little or no difference. Have also used Redex fuel treatment with no noticeable improvement. Would be grateful for any suggestions. Thanks.