The turbo has been making more of a groaning noise rather than whistle since I bought it. It also seems to change tone abruptly when the draw on it changes. This morning I started it and there was a little bluey white smoke but when under load there was plumes of white smoke. The turbo was delivering power though but I've no idea if it's down on power or not. Theres no warnings on the dash either Its a 2.0 tdi 170 brd engine on a 57 plate with 52k on the clock (seems genuine as all paperwork and mots tally up). Could it be something like an air leak or am I just in dreamland and I need a new turbo?