I will start by saying that although I have checked a few different things, if you have any doubt about something, I'd be more than happy to check again.

Issue: Most of the time, when I step on the gas, it won't want to rev above a certain point. If I slowly let on the throttle, then I can slowly get more revs out of it, but if I just put the pedal to the floor, it won't want to rev very high and sputters. Most of the time I drive it, it does this, but every so often it runs perfectly fine, but that rarely lasts long before it does this again. It has gotten progressively more common. Here is what I have checked / replaced:

* Fuel
* Fuel pressure is at 3 bar during idle and 3.5 bar when throttle is opened.
* Fuel filter has been replaced (Old one was rusted and the fuel dripping out of the old one had a nice orange color to it)
* Fuel injectors have been replaced after replacing the fuel filter and seeing the rusty fuel coming out of it.
* Vacuum
* I have replaced a few different vacuum lines that were questionable, including the one that goes to the MAP sensor.
* Spark
* Spark plugs are reasonably new and gaps have been checked and adjusted. I did just learn that apparently using the circular gapper tools can damage the plugs if you use them to leverage against the center electrode (which I have done, so I will be replacing these asap)
* I put in a new set of spark plug wires
* New distributor cap + rotor
* Compression
* I have checked the compression on all cylinders and three of them read at 210 psi (14.48 bar) except for one that read at 220 psi (15.17 bar) after cranking twice for each reading. I repeated the test twice for each cylinder to make sure my readings were accurate
* Air
* I have cleaned the throttle body as well as thrown a new gasket on
* I have sprayed starting fluid around the intake hose and accordion and haven't found any leaks
* O2 sensor
* I did have an exhaust leak upstream of the o2 sensor, but after welding that shut, it still runs poorly and still gives a code 2-2-1 which says to 1. Check the o2 sensor, it could be faulty or 2. check the air intake. The o2 sensor is newer, and I have read the voltages from it while it's running in the video linked below.

* Other
* I have verified the TPS to be working properly.
* I have checked my valve clearances and found them to be out of spec. I am currently waiting on the valve compression tool, so I can change the shims.

* Exhaust
* I chopped off my cat and banged it out because it was rattling, and I thought it was clogged (it likely was). I then welded it on very poorly, but there isn't any leaks upstream of my o2 sensor, aside from a minor one on my down pipe near where it mates with the manifold. My 2nd muffler was rusted very badly and started sagging, and I was able to just pull it off with no tools, so I just have the one muffler.

Linked is an album of images and videos relevant to my troubleshooting.
https://immich.tomfoolery.online/share/0bmdWnIZ6Jhh1fEFm6m8o32w6vk_vX1v04AJuVHNTMLN0--TNokPhtf9-8e-FXTEkZ4