could be one of 2 things mate

1 egr valve is sticking open at the wrong time , ie when your on the power instead of off and engine is trying to run on already burnt exhaust gasses

2 tdci pumps have an advance control within the pump which are prone to stick due lack of luricant in modern diesel

both the above would give you the "pinking" sound you describe and lack of power

blank off the egr valve and give it a go , if its the same your looking at the pump


john