Hi, I'm having issues with my T5 1.9tdi BRS for a while where I get blue smoke when the engine is under no load and reving or idling for a while. I can tell the oil is coming from turbo into the intercooler pipes and the being burned and creating blue smoke. Once i accelerate and burn it off, there is no smoke under acceleration but the exhaust still smells bad. I have checked turbo and had pretty much zero radial play but noticeable axial play so I have swapped it for a reconditioned unit with some radial play (normal even on new units) but no axial play. Also the old turbo wasn't as free spinning as the new with oil in it so probably bearings clogged with carbon I guess. Anyway, I also had higher crankcase pressure as it was pushing some oil fumes through rocker cover gasket so I guess the turbo issue is related to the higher crankcase pressure and pushing oul through turbo. The thing is, on idle the pressure is okay, oil cap is jumping a tiny bit but nothing major especially when compared with some online videos other people posted. I have also checked the the cat with endoscope and found that it is fairly clogged with soot, probably half clogged. My question is: Can the blocked cat cause back pressure in the exhaust that would push gasses into the turbo and increase the crankcase pressure via the turbo oil drain and push oil out into the intake via the turbo as well? It might sound like a lot of sci-fi at this point but it kinda makes sense as the smoke is only when reving with no load so no pressure in the intercooler pipe to hold the oil in. I know the high crankcase pressure can be caused by the faulty CCV (by the way, new camshaft cover fitted over a year ago) and also high blow by but the van puls strong and idle bit shaky but nothing I would call excessive for an old engine with 200,000 miles. I have not done compression test yet as need to order tester kit but wanted to know if anybody encountered anything like this before. A friend of mine had similar issue on a diesel Peugeot where new turbo was still passing oil and the issue was clogged cat in the end, just as I'm thinking it is here. I have ordered new cat so this will be replaced in next few days but still wanted to know your thoughts. Just to mention, head gasket was blown when I bought the van, I have fitted brand new head and pd150 bolts and had no coolant pressure since. The intercooler was also blown when I got it. Also, the start is bit rough especially when cold with puff of white/blue smoke but I thought that is probably some oil from turbo accumulated in the intake that doesn't ignite well when cold and after 2-3 seconds runs fine. Attached picture of my cat. Thanks for any help.