slight boost issue

hi all i bought a octavia vrs 1.8t about 3 weeks ago with 82000 miles and full skoada service history. the paper work shows it had a new turbo fitted at 64000 miles it said turbo bolts loose again new turbo fitted. i can feel the turbo come in about 2000 rpm but then it seems to hold back a bit. it then pulls holds back pulls and so on throgh the rest of the rev range. i also noticed it smokes very slightly i thought it was just where it was cold but it does it even when the engine is warm. i dont get the engine management light up though. i have read on hear about changing varius bits and bobs but i over streched a little bit to buy the car so can not afford to go changing them all. has any one had the same problem or does any one know a good place i can get it looked at in kent that wont charge me a fortune. many thanks melv