In August, I got a CEL which I believe was P0464. Had it reset and it stayed cleared until the CEL came back on the 19th on the way back from U2. Took awhile to get the codes read, but this time it was P0457 and P0464. Tried to do some research today, but it seems most troubles came from Impreza turbo owners where a pressure valve hose pops off a blue Tee behind the alternator. Well, the H6 doesn't have that, so I am,looking for other more-likely causes. 192K, and pretty sure I need to do the PCV, although I haven't searched the "how" on that one.