What the heck is that sound?

NOBLE|370Z

I have a GTM stg 2 TT kit on my Z. I recently had GTM 3" downpipes installed along with my new 3" FI exhaust with external WG (non re circ). Since then I notice this really loud noise coming from the driver front side of the engine when I'm cruising and accelerating at highway speeds. I know what you may be thinking - it's just the sound of the engine as the external air vented WG open. However I'm pretty sure it's not that since it makes a sound that is distinct from the engine noise and it does it at low or no boost.

It sounds to me like a spitting exhaust leak but I don't have a trained ear for that sort of thing. My mechanic spent 15 hours trying to get the gtm pipes to mate with the FI so I'm wondering if he didn't do the job properly. Tony at FI told me that the GTM downpipes usually have fitment issues so I was expecting it would be a PITA for my mechanic (which it was).

Could you guys listen to the noise in the video and let me know what you opinion is? Am I on the right track? I've already had to have my mechanic tighten the exhaust assembly twice but it's not fixing the issue.

Here's the video:

http://youtu.be/c7LliqOFrqU


NOBLE