The maf isn't really used much in idle, its too slow to react. The ECU assumes a certain air flow, but does pay it some attention. Dirty throttle body can cause idle dips on start up while the idle valve adjusts to compensate. I think it remembers the position though, so reving should be ok after start up.
Sounds like a weak mixture caused by potentially:
1. Air leak post throttle body
2. non functioning dump valve (does this happen after acceleration/boost or reving parked up?)
Idle runs very lean in closed loop mode, so makes any air leak worse, if you disconnect the throttle switch it might stay running because it will be richer, but it just a bodge.
Last edited by TonyS9; Jan 11th, 2019 at 16:51.
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