When i step on the throttle, around 4000rpm, i get overboost which is fine. After that though, when i lift my foot from the pedal as the car slows down, i get a half engine yellow light. The car i believe gets in limp mode and i cannot get overboost, generally it seems as if the car has lost its power. If i pull over, shut down the engine and start up again, the yellow engine light disappears and driving power is back again, but only just for once because if i push it, the same story happens (yellow half engine, lack of power, no overboost etc.) until i shut down engine again etc. There is no error code diagnosed when using Torque from my smartphone, isnt this strange?
My experience has been that if there is a leak from the airbox to the turbo that you'll get a check engine light on the center console, not the half-engine one. I busted my inlet hose and learned that one. That was a simple fix. So far for me the half engine light has only come on for issues in the turbo itself (busted waste-gate) or a massive oil leak (it bled out on to the street one day all at once). I'd start by looking at the fittings from the airbox to the turbo, see if they're all tight and that you have no cracks or loose connections. Check the crank case vent hose as well, as it can get loose sometimes. It branches from the inlet hose to the top of the engine. After those simple checks, you'll need advice from someone with more expertise than me.
I'm not familiar with Torque, but generic OBD2 scanners won't see proprietary MINI codes. You'll need to find a tool designed specifically for the MINI to see all of the codes.
Thanx, can you mark on the photo im attaching where to have a look for the things you suggest? Im not aware of the terminology, so it would be very helpful if you could mark on the pic!
Make sure these fittings are tight. I'm still kind of leaning to something a bit more serious though. Hopefully someone with more skill will chime in.