white smoke
white smoke is burning off coolant in exhaust system,its why i think you should check all your coolant hoses,fallow each one to see where there leading to,you say engine rebuilt lately,this is why im thinking its just a wrongly replaced coolant hose,it happens,as B4 twin turbo,s have an abnormal amount off hoses,and would be easy for somebody to have fitted 1 in wrong position,i have seen a guy fitting a coolant hose into a vac hose position,this caused coolant to flow through to exhaust system,i replaced all hoses in correct positions for him,put new oil and filters in car,and car has run perfect since,its why i recommend you do this first before giving up on car.