Got a P0300, P0171, and P0174 today. I should add I reset the ECU last night because I had my stock cats re-installed last week, and noticed the idle was a bit rough. But there were no codes up until today.

I took the engine cover off to check some stuff, I noticed there's a vacuum suction right in the center where the engine cover bolt would go. Is this normal?
I just randomly noticed it, if I put my finger over it, there is definitely suction, and the sound goes away

See pic below:

 

I think you have found the problem! You have a intake vacuum leak. I suspect someone may of used a bolt that was too long and cracked the intake. Have a close look for cracks or is the brass insert is raised up.

Code Definition:
P0300: Multiple cylinder misfire
P0171/P0174: Bank 1/2 too lean

Misfires are usually the result of a lean (extra unmetered air, like a vacuum leak) mixture.
The ECU tries to add fuel (I suspect your fuel trims are VERY high) until a set limit, then it throws the P0171/P0174 code.

 

Thanks! So if this is the case (cracked intake). What am I looking at in terms of repairs. Can I just seal it with something temporarily. And yes, the brass insert is not straight, it is angled.

 

I would:
(1) Insert a bolt into the metal insert and see if you can remove it or raise it up
(2) Using a 2 part epoxy for plastic (maybe: PlasticWeld Epoxy Putty | J-B Weld) mix up some and apply a little to the insert and around the intake manifold.
(3) Push in the insert until it stops. It should now be strait with a little epoxy squished out around the edges.
(4) Let the car sit for the required time, as per the epoxy instructions.
(5) Start the car and check for vacuum leaks.

In the future, be VERY carful when you tighten that bolt.

Good luck!