Hi Ben, I still haven't had a chance to get the car logged again since I had some work done on it lately so not sure what state it's in yet. It's going on the rollers at a local RR day next week tho so hopefully that will show what's going on.
From what I've read about boost leaks, depending on the exact circumstances they can be pretty bad before the ECU realises something is up. That said, 0.2 add. fuel trim doesn't sound like much? I thought the tolerance was +/-10?
Given your fuelling is out tho your g/s may be a symptom of that, in as much as the ECU may be cutting back the requested boost to prevent things getting dangerously lean. Just as a test tho, have you got or have access to another air filter (even OEM box and panel filter) you can pop back in just as a test?
The only things I got done that could feasibly affect this were new spark plugs, fuel filter and injector seals, this thread's so long now I can't remember if you've tried all those or not! I know you were talking about spark plugs at one point tho so maybe it's not that but mine hadn't ever been done that I can make out so did them anyway.
I'll be sure to post back here if I have anything to report, let us know how you get on at Forge tho.