Noise from engine compartment Options

[mkernz22]

Alright, so this noise started to occur in the engine bay a few months back and I've been starting to get annoyed with it. It's not a constant rotating noise, but it only happens at about 1,600 RPM's. It is definitely a rattle of some sort, but I can't tell where it is exactly coming from. I have only 2 thoughts on what it could be, either the exhaust rattling on the cross member / sub frame or the front / rear engine mounts are bad. From what I know, it might still have the original mounts still in there because they looked kind of old when I had the engine out. Also, I did put the poly inserts on them, which is why I think it would most likely be the engine mounts. I have a video so you guys can hear it, don't mind the sound from the intake.

[mkernz22]

It only does it at 1600 rpm's, nothing higher, nothing lower. I don't have a cat on the car, and it's definitely not the intake, or do you mean the manifold itself?
The only two reasonable answers I can think of is that the exhaust is hitting somewhere on the car (being that the flex section was F-ed up when I got it and had to get it chopped and extended in some places to fit properly) or the engine mounts. I'm going to jack the car up tomorrow and just take a look at the exhaust