hilux 3.0L turbo 1kd 2006

Hi Guys, hope someone can help with this problem. This engine has a very audible engine knock(sounds like a fuel knock). It is worse under load between 1200-1800 rpm and when engine is cold. At operating temp the knock is there but not as loud. I have taken it to the dealer and they diagnosed faulty injectors which they duly replaced but with no improvment. They said no fault codes were recorded.
The vehicle has travelled 11000 klms. the knock started to about 6000 klms. Has anyone come across this or any clues as to what to check? any help will be much appreciated

Cheers