Knocking noise with video

[JuSteve]

I've been around the forum doing some troubleshooting and I can't quite figure out what's going on with this engine noise. The video is at the bottom. Hopefully someone can listen and tell me.

Here's the breakdown

2004 WRX and it's a salvage title. I've gotten pretty much everything sorted out except for this one thing. There's 39k miles on it and as far as i know, the only mods are a lightened flywheel and the guy a got it from said there were cams in it. It does idle rough but certainly nothing like a 454 big block. There's also been a P0301 cylinder one misfire code popping up that I can't get to go away. I had it in to a subaru performance shop in denver and they fixed a couple vacuum leaks and gave it a basic tune. It put up 202 rwhp on the dyno so I figure all 4 cylinders have to fire but something tells me the timing is off. I put in a new MAF sensor, swapped out the plugs (even though none were fouled out), gave it some good fuel injector cleaner through 3 tanks, run 91 octane, and haven't raced it.

I was really hoping to turn this into a rally car but if it turns out to be more trouble than it's worth, I might pawn it off on the next sucker and get a new one. My dad and I have a pretty extensive knowledge about cars but it's mostly been on carbureted motors. ECUs give me trouble. Is this something I can fix on my own or should I take it in to professionals? Or dump it..

YouTube - WRX engine noise

[Donkey]

IF YOU HAVE A MISFIRE CODE ,PLEASE READ THIS!!!

I'm not sure why it would have a flywheel and cams with not other mods. That sound is a rod knock.

[SD_GR]

If you're lucky it's a tensioner but it's more likely a rod.