Just to share my exhaust manifold crack due to 'vibration' from the downpipe(exhaust fabricator use short type stainless flexi hose-so when wot and engine move to back and forth the whole exhaust system got pull/stress)
When wot can hear the whole front engine resonannce/vibrate like 'zzzzzz'inggg. Fix the crack by welding and change the flexi hose too long type.no more weird resonance during wot.
Sound like tractor at idle,actually its the exhaust pulse come out from the crack area.(maybe due to my hicam also as the sound goes in pulses)
The drop in power at 5k rpm might be the pressure inside the turbo manifold was abruptly reduce from the leak area to sustain the turbo rpm/boost