Grinding type noise at certain RPM's while on the throttle.
 

Alright guys, first time posting because normally I find all my answers by searching through the threads but for whatever reason, whether I'm dumb, or just can't find it, just looking for some potential answers on this problem.
So I have a 2003 Infiniti G35 coupe 5AT, non- stock, with an unidentified grinding type noise. Noise seems to be coming from the front passenger side area, and makes very distinct metal on metal type grinding noise while on the throttle and only at certain Rpm's. Let off the throttle, the noise goes away. Seems to be more prevalent at specific speeds and RPM ranges such as 40mph and 1800-2000rpm and most noticeable 60ish mph and 2100-2300 rpms. At higher speeds than that, the range seems to widen, but yet again, only while on the throttle. Doesn't seem like a typical wheel bearing noise, plus I changed out the entire hub assembly for the front passenger side a year ago due to a bad wheel bearing at the time. Also, while at cruising speeds, if I put it up in neutral, and hit the same RPM ranges the noise is nonexistent. It's very odd to me how dependent upon being on the throttle the noise is. There's no hard gear shifts, or any typical transmission issues, nor do I notice any other vehicle impairments. But obviously, a metal on metal type grinding noise is always concerning. Hoping you guys may have some answers! :confused2:

I've had ringing/grinding type noises due to exhaust leaks, which will sometimes only manifest when the car is under load. It's probably worth checking your flex pipes for damage.

I can almost guarantee it is something with the exhaust system, there are heat shields on both the catalytic converter and the y-pipe that are notorious for making that exact same kind of noise that only presents itself at certain RPM or certain load ranges.

well, considering I'm slammed, I don't get much ground clearance as it is and have been through two y pipes already and know that one of my Flex pieces is leaking again, it's just always been a noticeable exhaust leak noise though which is why the other grinding noise concerns me. I'm going to lift it, and look at it everything again though and see if maybe a heat shield or something is making specific contact somewhere. The new sound is just weird though. It's almost like an internal grinding type noise. Plus I'm straight pipe with test pipes so there's no cats anymore.

that's the only thing that concerns me about this new noise, is now that I'm straight pipe with test pipes, and a Stillen y-pipe, those Factory heat shields are no more. It almost sounds like grinding in the diff, but what is confusing me is it's coming from that front passenger side