Fitted an Sti top mount the other week, all seemed fine but yesterday when out the cars dump valve wasn't as loud and didn't sound like it was dumping the same. Was making a sound more like a hks ssqv/turkey chatter noise then dumping from the turbosmart supersonic. Still seems to be making boost on the gauge.

I fitted the standard valve back on but can still hear abit of a chatter/noise when I lift off.

Boost or vac leak maybe?

 

Check all your pipe work and no leaks in the intercooler.