Alfa Romeo Repair: poor acceleration, model designation, vacuum line

Question
Fuel filter changed, pump checked and ok suggested by mechanic may be a turbo problem. He says turbo appears to be working ok but dumping force through  wastegate  overflow. Does this seem likely ?  -------------------------    Followup To    Question -   I have a 156 2.4jtd (2000) experiencing poor acceleration on moving from standing start with revs initially dropping when applying power and then very slow to pick up speed.Also speed topping out at just over 100 mph at only 3000 revs.Otherwise driving fine smooth and resposive between 2000-3000 revs and idling with no probs.Any suggestions please    Answer -   I would first change the fuel filter and then run a volumn and pressure test on the fuel pump.  Note: checking the pressure is not enough--the pump must also produce enough volumn (.5 liter/20 seconds or so).

Answer
Yes.  Turbos do alter the diagnoses.  A stuck wastegate very well could cause the problem. Or it may not be stuck and a sensor is malfuntioning and causing the wastegate to stay open.  

I am in the usa and do not have access to newer data.  Looking at the model designation carefully, if this is a diesel look for a clogged vacuum line off the intake or exhaust manifold to a pressure sensor.