I haven't looked at mine yet, but I believe that there is a diaphragm in the top of the loo roll/vortex type filter.
These can also become blocked, I will be doing my service soon, so will check..
this diaphragm is in the top cap that is bolted on.
Greg.

I towed the horse trailer today and the car is still smoking badly. I will try blocking the vacuum line to the EGR valve but I might have to resort to an EGR delete kit if the valve is jammed open.

I suppose it could still be a faulty injector, although they were reconditioned not very long ago.

Block it Glen, it doesn't take 5 minutes, and you'll have a new car.
Then you can fit the egr delete kit, the egr gets full of crud and crap.
Greg.

I think I have found the cause of the smoke, and a few other issues too.

As well as the smoke recently the car seems a bit down on power, it seems to be using more fuel, the turbo has started making a whistling noise, the revs seem to rise and fall sometimes, and there was the apparent oil leak below the EGR valve.

Looking on the forum today I found a post where a guy had the same black smoke issue and it was caused by a split air intake hose between the turbo and the intercooler. The interesting thing was that he had noticed oil deposits in the area first and this led him to the split hose. So I rushed outside took off the engine cover and checked the underside of the hose leading into the EGR valve and, sure enough, there is a split in it about 1 1/2" long.

I am hopeful that a new hose should sort out all of the aforementioned. I have been looking at where to source a replacement and it seem that to buy the two hoses and metal pipe that go from the intercooler to the EGR valve is about £130 + VAT for a genuine part. Alternatively I can get a set of all four hoses (turbo and inlet side of the intercooler) in black silicone for £95 inclusive, and I guess if one hose has gone then the rest are likely to fail too.

I will probably fit an EGR delete kit at the same time as the hoses.

Well spotted mate.

I fitted the EGR by-pass and the silicone hoses between it and the intercooler yesterday.

The silicone hoses were a good fit, and the clamps were very good quality, although it took a bit of figuring out as to which hose and clamp went where. The hoses retain the original clip on connector to the intercooler but for this connection I had to use the original jubilee clip, as the new one was too wide. I ran out of time to change the ones between the turbo and the intercooler but I will do those soon.

I have only done a few miles since but the car seems to be running better and it is not smoking as much as it was. There is still a fair puff of grey smoke when I initially floor it but that's it.

The only problem now is what I thought was a whine from the turbo because of the split hose, actually appears to from one of the fuel pumps, probably the one in the tank.

Mine was a whiny old git too... but it never stopped! It just started one day for no reason and 18 months later it was still whining  Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

I am slightly nervous about it, because the one on our old TD5 Discovery failed completely shortly after it started making a racket.