Just a regular stock GTB twin turbo engine bay... stock BOV, stock airbox (K&N panel), everything clean a tidy, replaced intake pipe 3 months ago, and all vacuum lines. Was running very nicely after that.... smooth and 11/15psi boost.
Yeah, all subaru's I've owned have had that slightly irregular idle, where it shakes ever so slightly every so often. But this is not that. It shakes constantly, changes exhaust tone, and misfires/stumbles on partial throttle anywhere between idle and 0psi. Then under boost it takes off and has no noticeable problems.
I'm wondering now if it has some headgasket or valve issue. Leakdown will reveal that I'm hoping.
Doesn't seem to be knocking. Data for "Knock Correction Advance (degrees)" and "Knocking Signal #1 (On/Off)" was all zero's for the time I logged it on cold idle the other day.
Gotta find time to swap out the coils and plugs and injectors systematically, to rule them out. And fuel pump. Hoping it's one of those!