Rover streetwise turbo issues

[Stupid face]

Can any one help have a rover streetwise 2004 diesel 2L there is lack of power and ecu light was on constantly have changed oil filter oil air filter hoses tightened and fiddled with actuator no whistling with turbo just lack of power then power kicks in 3000 revs ..ecu light now of.......please anyone have this issue

[Stupid face]

After power lose , but didnt actually do anything to it .