What you describe sounds sorta like what happens when the 1.4T's pull timing to combat knock.
If you're running 87, try going up one gas grade and see if it makes an improvement. I thought they'd mostly fixed it by the 2016 MY, but if it still continues, check spark plug gaps as well - they should all be gapped to 0.028" and were wildly inconsistent from the factory in the earlier years.
If you're running 87, try going up one gas grade and see if it makes an improvement. I thought they'd mostly fixed it by the 2016 MY, but if it still continues, check spark plug gaps as well - they should all be gapped to 0.028" and were wildly inconsistent from the factory in the earlier years.