Re: noise from car, could be the lack of resonator box making a hissing noise. The resonator is that, it's there to dull the induction roar.
Important:If it has been removed what is the air filter piped to from the bottom of the OE airbox? Is the lower horizontal pipe still attached to the bottom of the airbox? I only ask because if there is nothing there, then the inlet is at water level! The induction must be free from water ingress, therefore an open hole low down will suck water in big time and you will suffer hydralock, a scrap engine.
Full OE kit is as this:
Resonator to the left, airbox to the right, connecting pipe between the two.
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