So my Forester has been running fine as a daily up until recently when all the sudden it began to idle extremely rough, even dying. It seemed to clear up when driving though. Then a p0011 CEL showed up. I pulled the banjo bolts and found the screen on the one on the top of the driver's side head was obliterated. After removing that screen the code went away, but the idle is even worse now and my AFR is around 16.8:1 at idle, dropping to around 15.3:1 when revved. Any ideas where to go from here?

Anyone?

you should log the avcs cam angle- you could have debris stuck in the AVCS mechanism which could jam it in place at an advanced position. could also be debris stuck in the oil control valve.

What angle should it be at? I'm assuming under 10° advanced at any given time?

I've always heard that making sure the left and right were more or less synchronized is an easy check.