I bought my 52 Plate TD4 about a year ago and still have not got it on the road. The biggest problem is a knocking noise coming from what sounds like the top of the drivers side. I replaced the rocker cover gasket and checked the cams which look alright. I thought I had found the problem when I found that an injector had been changed which had different serial numbers on. Turns out it was for an automatic TD4. Changed this injector for a reconditioned one. Still knocking! I have tested the fuel return on the injectors and cylinders 1 and 3 have about a quarter more fuel return than cylinder 2 and 4. I have fitted an ERG blanking plate and this has made no difference. It starts easy but smokes quite bad. I did run it up the road the other evening and the power seems fine. Does it sound like a fuel problem or am I getting fixated on this as being the problem? Thanks for any help you can offer.

What colour is the smoke?
White, black or grey?
What happens when it's fully warmed up?

Thanks Madmustand. It seems to be a whitish blue smoke. Once it is warmed up it still smokes when it is revved. I have had a friend come around this evening with his computer. He said it is diesel knock which I thought it was. A screen shot I was sent shows a Data Stream page with each cylinder listed. The readings are;
Cylinder 1 6.50
Cylinder 2 8
Cylinder 3 10.69
Cylinder 4 13.59
Above the numbers it says value. I have no idea what this relates to but he did say that the injectors need coding to the ECU. Im sure I have read on here that they don't need coding to the ECU.

Those readings should all be as close to zero as possible.

It’s an indication of the amount of fuel injected to maintain a stable idle.

With the leak off test and these readings my first port of call would be injectors - but without seeing it first hand it’s hard to tell if there’s another issue