[Run to Rund]

If the wastegate on the exhaust housing is stuck open, you will not build much if any boost. You WILL NOT get full boost all the time. You will not get a howling noise. Howling can come from a leak in the compressor discharge system toward the engine or, more likely, bad bearings, etc. causing the compressor wheel to wobble and get too close to the compressor housing.

The purpose of the wastegate is to regulate the maximum boost pressure. When open, some of the exhaust gases bypass the turbine wheel and thus don't contribute to developing boost.