I have a 1993 Scoupe turbo. The wastegate solenoid is either broken or the hoses are connected incorrectly. When the solenoid is not energized, the air that comes from the turbo is routed to the wastegate resulting in low turbo pressure.
This is how the solenoid looks like:
Maybe someone with a Scoupe turbo can have a look to see how the hoses are connected? The solenoid is located under the battery. You can see how the hoses are connected without removing any parts from your car.
The online service manual (thanks Hyundai, this has been really helpful several times) is not correctly describing my car in this particular area. In the manual, the solenoid is not connected to the pressure side of the turbo but to the manifold. This might be explained by model differences between the cars from the US and the Netherlands.
Rob