RX8Club.com - Rx-8 Misfiring?

Alright, so this is my first post and I was just looking to see if I can get some insight as to a problem with my '04 Rx-8 6SPD.

So, I bought the car at 110k miles, roughly. Sadly, with it being my first car and I was 19 and eager to get my first car, I did basic checks on it before buying it but couldn't not get a compression test done. As far as the symptoms, it was all clear. But more on that in a second.

Now my car is at 117k miles. And my car has started misfiring. I took it to Autozone, got the codes read and surre enough it popped a P0300 and P0302. It first did it on an hour and a half trip from another city. And it went away. But after that, whenever I'd floor it, sometimes at the high rpm range (6500+rpm), the car would hesitate but still climb, and it might throw a flashing CEL (usually it does). Or when I'm on the highway and around 70+ mph and give it a fair amount of gas it would also misfire. Flash a couple times, etc. Sometimes it would just happen if I was going above 70 and not give it gas.

But as of yesterday, I started driving it pretty hard to see if I could get it to happen again and sure enough, it did. But this time after the CEL flashed, I tried to floor it above 60 and it barely had any juice. Nervous, took it back home and let her idle. She if misfiring because the exhaust will do that occasional air pop that comes with misfires. Her idle wasn't too rough until that happened yesterday. At first she would just go to around 700 or so rpm and bounce up to 8 or 900 and repeat. But yesterday it seems like it'll go to around 500 even and then bounce up.

Since the misfires started, ive done the basic checks and fixes. Such as:
-Cleaned MAF sensor

-New DML "Racing" wires and coils

-Spark plugs replaced maybe 2k miles ago (NGK laser iridium)

-It has a black halo racing midpipe

- I replaced the rear o2 sensor, because the previous owner stated it was going bad. Weird thing is, when I took it out, it didn't look like an o2 sensor that I've seen for an Rx8. I'll post a picture. But I replaced it, and when I did the constant CEL went away but the cars still misfiring. If I replace the front one too (because maybe it's a weird one like the rear one and that could be causing the misfires), could that be a cause?

The only thing else I can think of is change the pod filter on my AEM CAI (its kind of dirty), replace the front o2 sensor as well, check the fuel pump, or face what's in the back of my head and a failing engine. Problem is I'm almost 20 and I'm broke. So if someone could help me out and give me a faint idea as to what to check next, it would mean the world. Thank you! This is my first post, so I'll post any more details if its needed.