Hi my 2007 1.6 diesel c30 is down on power feels like its not boosting. Feels like a straight diesel not a turbo diesel. There is no engine lights either. Engine running good no weird sounds or lumpy running. Any thoughts to what could be the problem

 

engine is in fault mode, or limp home, what ever you preffer, hissing is probably coming from pressure side of turbo, in otherwords a leak somewher
e. Probably why the engine light is up. You'll need to read codes