FWIW, on Jul 9 05 I used a can of Gunk motor flush when the car had 28,100 miles, then Nov 28 06 at 63,153 miles, then Aug 15 09 at 111,770 miles again on Oct 31 09 at 119,311 miles, then on Mar 17 11 at 141,800 after the P0011 and P0021 CEL.
I replaced the turbo at 142,200 miles
Used the Subaru flush at 144,300 Oct 1, 11
I haven't done it again. The new ej257 has about 16,000 miles on it. I replaced the short block because of oil usage, the bearings were quiet.
174,000+ miles, 5/20/12 new ej257 short block, 8/20/11 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. Also CHECK YOUR OIL, these cars use it.