I called 1-800-subaru3 today to try to get the piston slap I experience on cold starts on my 2000 Outback limited. with slightly under 51K miles, fixed.
I was told that it is normal, that it can't be fixed, that some have tried replacing the short block, changed pistons, tried various liquids or different octane gasoline but because of the design of the pistons, "they all fail". I was also told that the Subarus in their fleet in New Jersey have the problem. The bottom line: they won't fix it and it won't harm the engine, so don't worry about it.
So, I am curious, how many Subaru owners do in fact live with the problem?