MAP sensor not plugged in to anything?!?! MK4 GTI, 1.8T, SMIC,

[h100vw]

throttle position mapping doesn't work too well in turbo cars because the air flow rate is not predictable enough. If u plant ur foot, initially there is no boost until the turbo responds, so the air flow is low, as the boost pressure rises, so does the airflow and therefore fuel requirement. but the throttle is still in the same position - so throttle position alone is not really enough information to accurately calculate fuel requirement (it can be made to work on non-turbo cars, but isn't used often as it is too sensitive to environmental changes ie. heat, humidity, changing the flow rate for a given throttle position).

If the MAF is bad for whatever reason, boost is restricted and it goes off what it knows. Throttle position. The fact that it isn't a very accurate way of determining flow is why they run rich.

Also the reason that the ME7 has a MAP sensor as well as MAF.

Gavin