I recently acquired alegacy GT-B BG5 and there is a honking sound similar to a trumpet at while accelerating at low RPMs (before the switch over point of the 2nd turbo)I was wondering if anybody knew the cause of this. It does not always happen andsometimes there is a slight hesitation when the honking sound is heard

 

Take your hand off the horn?

 

the standerd dump valve will be leaking??