Toyota Previa 2003 D4D turbo

[Saladcream]

Hi first i would like to say what a great forum this is. The information i have learned in such a small amount of time has been great. 

Now a little about my car. Its a 2.0 D4D 130k miles. When i bought the car i noticed the turbo not kicking in. No problem i thought since i am not afraid to look into issues on a car. I cleaned the egr replaces the fuel filter serviced it etc. Same problem. I then replaced the MAF sensor after the MIL illuminated. Despite all of this the turbo didnt kick in. I then researched on the internet reading about other owners with similar problems. However reading through many posts the issues described by other oweners are not similar to mine. 

My issue is slightly weird. I have no codes and no lights on the dash. The car starts fine when warm and cold. There was a period of around 2 weeks when the car drove faultless, the turbo kicked in at all speeds and gears. I mostly drive the car on the motorway. Now when the engine is cold the turbo works perfectly. By perfectly i mean if i accelerate the turbo kicks in straight away and pulls in all gears. As soon as the engine reaches operating temp the turbo refuses to kick in which makes driving it very frustrating. I am completely stumped and dont know what could be causing this.

Any help will be greatly appreciated.

Regards Hasher