So my 2008 Impreza WRX keeps throwing p0011 and P0021 codes, now I have already read through numerous posts about this issue and I am aware of what the codes mean and what normally causes it for most people. For me however this is on a freshly rebuilt engine that has only done maybe 1000 miles and the oil and oil filter where changed about 250 miles ago (Bosch filter and Castrol Edge 5w30 oil).

The CEL comes on after 2 cylcles/journeys and stays on and the codes always come together never just one or the other. I have double checked all of the oil line filter meshes and they were all removed when the engine was rebuilt so no issues there, I also pulled the turbo off to check for any issues but that is still mint with no shaft play what so ever so I'm not to worried about it being an oil issue.

Today I connected my laptop via a diagnostics cable and FreeSSM so that I could see what was actually happening. Interestingly Freessm reports virtually no cam advance at any point, the maximum advance that it recorded was 2 degrees on one trip and then 4 on another but the OCV duty cycles varied with RPM/Load as I would expect. FreeSSM also shows the error as being Cam System Performance as oppose to Over advancing.

Any thoughts on what it could be?

I have got replacement OCV solenoids coming on Monday just to rule that out but both being faulty seems like a long shot.