We've been seeing this problem lately on LGT's and late model WRX (push style clutches). The noise is even worse on LGT's that install the WRX flywheel/pressure plate combo. The noise is coming from the clutch fork vibrating against the slave cylinder pin. It can easily be misdiagnosed as a bad throw out bearing. The trick is to drill a small hole on the clutch fork and install a spring to give the clutch fork a slight pressure against the slave cylinder pin (similar to pull style clutches).