well it could be either...
check your belts and make sure they're not loose, if soo tighten them up
if its your turbo you will find it starts squeling as soon as you come on boost
take off your accordian hose that has the other 3 pipes routing into it off the front of your turbo and just check your compressor wheel is still fully intact... see how much side play and back and forth play it has... don't force it sideways or in and out... just give it a light wiggle ... if she's got no play or very minimal i wouldn't worry... also check that it spins freely
let me know how you get on with that so far and we'll continue
