2.5di running problem

[bigbrother3269]

Hi guys-newbie here and a little cheeky at that...i got a Ldv Convoy 2000w fitted with the transit 2.5di engine,brought it 2 months ago and after having spent the last 4 weeks rectifiying all the bits the mot tester missed(!) i'm having some minor issues with the engine/performance.
I've got a lack of performance around 50mph onwards and occasional flat spot about 30ish...also i've noticed a bit of black smoke under acceleration at mid range/top end.i've serviced the engine-done new cam belt etc and double checked the timing-replaced the injectors and filter,done the egr mod,checked fuel hoses etc etc.i've noticed on this forum site a bit about the fuel pump and the piston on top-is there anything else i should be looking for or at?
thanks

[AndyG]

Well the only thing left is what you've mentioned and that's the TORQUE SLEEVE