Oil use

My engine is using a lot of motor oil . Allthe spark plugs are light gray , and there is no deposits on them, and I can't say the exhaust is blue. If I unscrew the tube form the air filter to the injection mainfold , the surface around throttle valve is black , and seems oily. Could this be caused by a malfunction in the oil separator system ? Anyone with the same problem ?

Have you checked to see if the flame trap has been removed. I believe that it should be removed to stop crankcase compression.

Flame trap 

I think it's supposed to be removed. It should be done on service. They decided that they were causing more problems than fixing so they instructed volvo dealers to remove them.