Advise please on 325tds

I have a 1997 E36 325tds.
It has had many problems from new. It's latest one is that it runs badly with poor power/torque and black smoke (Intermittently) . I have taken it to
a BMW dealer who has not diagnosed a fault, and they don't think it has a fault!
I then took it elsewhere not to a dealer, with limited success.
It idles at its worst when hot and humid, horrendous with the air con on. It still has the fault when cold outside just not so in your face. When you do turn air con afterwards, it still runs badly until you turn the car off and restart.
When stationary, it feels like it will stall - and has done on few occasions even tho the rpm is not low. Pulling away requires some concentration. When easing off the gas the car jerks around and will do so until the car is stationary and out of gear, it will stay ok for a few seconds then start again.
This has been going on for over 2 years now.
The other thing is, the egr valve leaks oil, and the internals get smothered, as does the inlet manifold. I have taken these off and cleaned them and the car runs almost ok, but after about 100miles its back to its old habits. It was recommended that I had the turbo taken off and cleaned which I have had done, with a slight increase in power.
I took the car to ATS to have tracking checked they were horrified by the cars problems (its fault was most definitely present then!) and suggested it might be the cat - im not sure, its alot of money just to see.
Help me please!!!!
Would be lost without my car, but it is pain in the backside
TIA
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A diesel has a catalytic converter?
Floyd
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See the garages review pages on my site, I suggest you find a good specialist.
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News wrote:

There might be air in your fuel system. The injectors could be dirty. Try having those cleaned, as well as checking fuel lines for cracks. In addition, it might be a faulty fuel pump (I believe that's what it's called, it's a large, silver, boxy object that sits on the port side of the engine: it feeds fuel to the cylinders). I don't think fuel pump error would pop up on the dealer's computer.
Fuel pump replacement isn't cheap though. Think 1,000 pounds and up.
It might help to try a few other garages. For example, Opel Omegas (Vauxhall Carlton?) used to use the same engine here on the continent. Range Rovers had 'em too.
Good luck.
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