Odd Noise Between 3-4k Rpms

[240dreams]

I just changed my oil and Im starting to hear a weird noise between 3-4k rpms. Its an odd grunt type of rattle. I can hear it in gear and out of gear so im pretty sure its not the transmission. I hear the noise when revving up and down. The noise seems to be coming from the front driverside of the car. It may not even be the engine but it does precisely happen only around 3.5k rpms. Someone please help me pin point this problem. Thanks in advance.car: 1990 240engine: blk top SR

[nismostate]

how does your oil pressure look?

[240dreams]

alright upon further inspection and lots of free revving, i realized that the sound isnt from the engine bay. its closer to the exhaust system somewhere near the cat (test pipe). Does the engine move around a lot at 3.5k rpms? I also narrowed the rpm range to right at 3.2-3.3k rpms. anyone else have this issue?