What can cause Thick Black smoke on a Corsa 1.3 cdti without the Engine light coming on? It also takes quite a bit of starting and the revs take a bit of building up. It does act like an Inlet blockage but i've had it apart with no luck.

I have been trying to fix this car for a while now and i'm sure it is some thing Ovious but i have tried all sorts to fix it and i'm having no joy.

I have ruled out Sensors (swaped them with a good running car and they worked fine), Timing (the cam and crank lock up spot on), Compression (its 350psi evenly across the four bores), Blocked Exhaust or Inlet (checked all inlet pipes for blockages or holes, tried running it with no down pipe on, new turbo fitted) EGR was replaced not too long ago but i don't know how to check it is working? i took it off and cleaned the soot out but it looks like new plus i don't think it would be able to cause the Thick black smoke? from what i read its more subtle than that when its stuck.

I am starting to think its mechanical but as the smoke is Black and the compression is 350psi (cold and dry) that kind of rules out Piston rings, There is no oil in the water or water in the oil and no excessive pressure coming from anywhere so that kind of rules out the head gasket.

Could of course be the ECU but when its pluged in to tech 2 it works fine so not sure about that.

I know the head gasket was replaced not long ago so could some thing be put back wrong like the gasket be on upside down or the head torqued up to tight and cracked or some thing like that?

I'm after things to try to be quite honist i have tried all sorts and not got any closer to fixing it....