I really hate seein this! It just boggles my mind that Subaru puts out a tune on these that they do. Anyone that has seen the stock tune can see without even a datalog that the tune sucks! REALLY SUBARU??? Give us a break. I've had a heavily modded WRX that put out 340 WHP and a stage 2 STI. The difference, a good tune. A friend of mine had this happen on his 08 STI, 15,000 miles later the motor went out again and the dealership wouldn't cover the cost so he ended up buying a new motor. Its ridiculous that the dealership Is telling you that forged pistons and a tune are the correct fix and yet Subaru will deny the warranty work is something happens. They're a billion dollar company that cant get something so simply fixed. I guess they don't like being showed up by a little mom and pop shop that takes a few extra hours and does it right. Very sad!
OP, push for the new block, if you can, even if you have to pay out of pocket a little for the product and work. You will be happy in the long run, trust me. If you need an additional source for confirmation, PM me.