Multiple fault codes but no CEL

[Neinris]

Alright, so I've done some research and I think I've narrowed down the culprits.
Just dropped about $220 US on both O2 sensors and MAF sensor. All Denso parts from RockAuto, I consider it cheap since they're all OEM. I didn't want to just replace one O2 sensor, since they work in tandem and I'm sure the other one is probably going to fail soon. She has over 140k miles, and I hope to put another 100K or so.
Also, I have an exhaust leak from my axle back, I've jerry rigged the muffler a couple of months ago, but it's not holding up. I convince my wife that I can't pass emissions with a leaky exhaust, so she let me drop about $300, including shipping, on a new muffler, I didn't tell that it's a Tanabe Medallion Touring-S exhaust. Hope they all get here before the weekend. I'll scower the junkyard this weekend or the next for an evap canister, that's just too expensive to buy brand new.

Here's the link to the site where I bought the muffler, it's the cheapest I've found: https://sparktecmotorsports.com/i-30...hback.html?v=1