Welcome aboard, Casper.
Given the age of the car, it is quite possibly the vacuum hoses for the turbocharger actuator that have perished. If they're easy to turn on the barbs, they're asking to be replaced. Vacuum pump is over near the oil filter, just replace all of the vacuum hose.
Of course, the actuator itself might be shot. After replacing the hoses, idle the car and watch the little arm underneath the actuator. It should go up and down about 2-4mm at idle. If it sits rock steady, it might be the diaphragm in the actuator or it could be sticking vanes in the turbo. If you remove the actuator you should be able to move the arm in and out. If you can't, the vanes are stuck. I doubt this is it, it doesn't happen often (that's reported here).
Another thing to try is cleaning the MAFS. Just a couple of centimetres from the airbox on the way to the turbocharger, undo the screws at the back and withdraw the sensor - it's a long flat thing with a small slot in one end. Whatever you do, don't put anything solid in that slot. Spray inside it with either electrical contact cleaner (Jaycar, $10) or MAFS cleaner (SCA, $18). They're the same thing, rebadged and resold for a higher price. Use either with confidence. If you have a oil-based air filter that'll be the cause.
One last thing it could be - the EGR valve might be sticking open. I doubt this is it, when the EGR valve sticks the car is hard to start. The fix won't hurt the car, will either do nothing at all or improve performance and economy. Remove the EGR tube from the inlet side of the pipe, make a copy of the gasket using >1mm stainless steel plate and accidentally forget to make the big hole - just make the two holes for the bolts. Apply a bit of gasket cement to both sides (Permatex Ultra Blue is best), whack it back in and forget about it.
