The hissing sound is normal and its from the intake, yes. I have the same issue
The vibration could be from the motor mount or yes the intake itself. I always had a vibration problem though and a bogged down feeling even before the intake or any mod I did to my car.
It's either your exhaust manifold (I doubt though), intake, or your fuel injectors need to be looked at....also your motor mount, main cause of vibration.