'04 KA24DE clicking noise???

[aknjk]

First let me say that it is on my 2004 Frontier and its a work truck and its out of warranty I drive alot. Now to the problem my motor has a clicking sound around 1500rpm you really notice this noise when the motor is cold and coasting down in gear. The sound clicks kinda like valve noise but only happens around 1500rpm and it gets quieter when warmed up. It only make this clicking sound around 1500rpm no where else and it won't make it when you are accelerating at 1500rpm. It only happen when coasting down. I didn't make this sound when new it started around 25K I now have 38K on the motor. Any ideas??