consistent misfire at 1800rpm
 

My 2006 2.0 TDI 140bhp estate has had a consistent misfire since I bought it 6 months ago. It only, but always, occurs when accelerating under load between 1600 and 2000 rpm. When the car is heavily loaded, or going up hill, it is very bad and the engine misfires a few times, or until the revs get up to 2000. I've had several garages look at it, the injector loom renewed, the fuel pump checked, and engine cleaner added to the fuel. I've been advised to sell it but the car seems fine otherwise and I'm bound to lose out if I sell and buy another. Any suggestions please? The car has done 60,000 miles.