nice work.... and well done finding a decent looking replacement.
I had a 300tdi do the same recently at number two piston. This was caused by coolant leaking internally in the cylinder head, down the exhaust valve and into the combustion chamber at number two piston. Bit disappointing at only 354,000kms. I've owned this car for 14 years and maintained it thoroughly/regularly. Bores in the block are still like new, but the block is toast as is the cylinder head.

