Engine rattle during acceleration at same specific RPM

This is the same problem we've been chasing down in the 13 persona for a year now actually in our car it sounds like a piece of plastic rattling against something that's turning It's more of a like a plastic shield is fluttering in the wind like a hummingbird's wing I know it's not but that's what it sounds like doesn't really sound like the death rattle that you get when the fires being extinguished by water in a cylinder unfortunately because we know what that sounds like real well. This is quite different after pulling the EGR cooler and related piping off this JDM engine and putting it into soak and clean a clot developed In the middle of the stainless steel cooler We cannot blow it out and get it to go through nothing so we got another cooler that we had in the shop tanked it and you can see daylight through it It's completely clear reinstall that and the car ran fine for about an hour sitting here in the driveway driving it up and down my 2 mi Long Street all of it then the next morning started rattling again right there is it transitions from Eco mode into power where the gauge turns red is where the rattling disappears or it disappears with your foot off the gas the engine predominantly not firing and the car running down the road in between that Eco mode range ev to the end of eco is the rattles zone. That should be some kind of clue but I don't know what it would be other than that when the engine is running and we can reproduce this sound in the driveway when the rattling is happening it is not the engine missing It doesn't seem like it's the engine's reciprocating mass it seems it's more between the engine and the transmission but it doesn't sound like a spring is bottoming out if you will It sounds like somebody sitting there with an ABS pan plastic and hitting on it very precisely with drumsticks It's very strange. When this initially started several months ago several months after the install of the JDM engine we park the car rather than drive it rattling and destroy it the first signs of this we parked the vehicle My girl got in a generation too and has been driving that for months back and forth to work because well it never fails runs perfectly I've been messing with the persona you know every so often just to see what I can see which has been a lot of nothing very disappointing to say the least. So rather than destroy it I play with it every so often for an hour or two just see what I can see can't see a thing I hate to have to pull the transmission out to look at the torque plate and I don't know the input shaft of the transmission seems completely foolish I guess it could be something behind the transmission plate motor generator one or two but I wouldn't expect it to sound like this I would think that would be more of a metal on metal direct contact type thing and this just doesn't sound like that or it's metal on metal and one of the pieces of metal is coated or covered in something that helps it not beat another piece of metal to death I don't know but this has been going on about 9 months now.

 

Can't hear anything but noise in the video.
What's in the glove box? Something in mine get's free sometimes
and it rattles. I just open them and move stuff around and it goes away.

The clips that hold the cables loosed and will rattle. I have that in the middle of the dash.
But the podcasts drowns it out.
It's not it to me to go through all that's involved in removing the dash cover to fix them.