Go fast parts, If it were a GT 5spd wagon maybe but not a auto, outback model. Not to mention a forged crank runs 2000-3000 and forged pistons are 700-1200 a set.
This noise isn't only at startup Tbucket its between shifts, and at free neutral rev it rapppps ocasionally. I am familiar with the piston slap startup. Subaru USA said in its tech bulletin that it would effect engine life by less than 10% I am not the lucky type.
Hoping though a crank turn and 90 in bearings from the dealer will get me rollin again. I will post pics of the tear down. most likely.