DESPERATELY Need Advice Fixing 09 Aveo5!!!!

[TheCanadianKid]

My 09 Aveo5 is making me go crazy! I foolishly bought the thing with a misfire in the engine. I read online a coil pack would fix it and followed through with the buy. It ran a little rough when I first got it and I plugged in a code tester and got a bunch of codes P0172, P0137, P2270 and found some advice online and bought some parts accordingly. It appeared to be a misfire which damaged the cat. So, so far I have replaced.

- Ignition Coil
- Spark Plugs
- Mass Air Flow Sensor
- Upstream 02 sensor
- Downstream 02 sensor
- Exhaust Manifold / Catalytic Converter

I have a bunch of new shiny parts in the engine bay but the thing drives worse then when it had the original broken coil pack in it. It hesitates and jerks and won't go up hill past 20km/hr. I've literally ran out of things to replace according to the code reader. All of the previous codes including the misfire I have got have gone away except P2270 which is referring to the downstream o2 sensor (post cat). And I've replaced the cat and the sensor!!! The only things I can think of are E-VAP leak or fuel issue which is saying the fuel mixture is wrong to the downstream o2 sensor and jerking the car around attempting to compensate. I am going to do a smoke test and fuel pressure test to see if I can narrow it down, which I should have done in the first place. Or could it be as simple as one of my 02 plugs/harness is fried?

I am going insane and broke trying to fix this thing haha! Can anyone give some advice on this pain in the butt? It would be much appreciated!!!!