2002 A3 1.8T

Sometimes my car wont boost past 0.5 bar at WOT. The boost is not jerky or irregular, it just wont go past 0.5.

Turning the engine off and back on makes it boost to 1.2 bar again. Its only happended a few times in the past year.

Its remapped with a full milltek exhaust, and some other minor mods that arent relevant.

Just wondering what could cause that kind of issue? It feels like the car forgets its map, and goes back to stock settings, if thats even possible.