10 minutes ago, Evolution13 said:

Lemon of an engine.

Absolutely!

In regards to the potential piston ring issue. We can only advise. Though, have you removed the injectors and used a borescope to inspect the cylinder walls? If you have any scoring then it would look like a ring issue. This would give you a better indication of whats going on, and if they are scored, then youll not be wondering anymore. But then this may also be delaying the inevitable of starting the dreaded job.

After reading and researching about the problem the past month or so, some seem to have gotten away with removing the pistons, cleaning and fitting new rings. But this would depend on a number of things, such as piston/cylinder wall condition etc.

When i was worrying about it, I thought about buying a second hand CUPA/CUNA block, having that machined 0.5mm oversize to match the new pistons, then swap everything over. Saves having the car out of action for longer, waiting for your original block to be machined. You could then get your original block machined with new pistons and sell it on, try to recoup some of the money spent to sort the issue.

Thank you verry much for advices!

Today i will start process and lets see how it goes ;)