could just be the charger noise, but you can check for boost leaks by disconnecting the boost return valve linkage, holding the boost valve shut for 1-2 seconds at a time, the system will pressurise and you can pinpoint specific leaks.
did you seal the blanking plate with gasket sealant stuff?
also get the new charger on and get the old one apart, its not hard to change seals and bearings, and you can sleep easy, knowing you havent got a potential time bomb.
if you are going to run without rebuild, then just ensure there is a guaze between the charger -> intercooler pipe and the intercooler, this will catch the chargers innards if it shits itself!