I've got a Vivaro 1.9TDI just had new turbo fitted,oil and filter,air filter,boost pressure sensor,fuel filter but now whilst driving in 1st and 2nd gear there is no power no matter how much I press on the accelerator and then all of a sudden it will just shoot off. I don't have any problems in higher gears. If anyone has any ideas what the problem could be would be much appreciated as i've spent £1100 on it so far.