i see. Cheers for the video drrollo, thats confirmed it cant be that...
Its sort of like something 'activating/deactivating' as you rev it past ~1500-1700rpm, which led me to believe the it was the dephaser (as the solenoid kicks in and out around that RPM range)...
Matty, its the inlet pulley, it has a solenoid on the top of the cam cover that changes the pulley position on the cam to alter the timing as you pass ~1500rpm.