NEWCASTLE BROWN

after a reasonalbe drive the other day sat outside my house, in neutral gave my legacy twin turbo the big right foot.on de- acceleration i notice a very small ploom of light grey smoke come from the intercooler scoop. strange i thought. so i opened bonnet and rev ed the engine to highish rpm again on de-accleration slight ploom of greyish smoke came from the turbo housing on right hand side of engine(looking at engine from the front of car with bonnet open) is this something to worry about? of just a sticky dump valve thing? car is standard as far as the engine is concerned