Your next step is to do a compression test. Make sure the battery if full, you can even do it with a charge on or a jumper from a friend just to keep the battery up, each cylinder you test will lessen the power of the battery.
When you get a helper to crank the engine, you watch the compression gauge, it should pump up quickly, lets just say 60PSI. Lets say on a cylinder, that first pump is already on the compression stroke and the first pump is low. Do it again. The first pump is what we call testing the rings.
Count the pumps as the compression gauge is pumping up higher and higher, what is the pressure at 6 pumps, some mechanics go and go until the compression is done getting stronger, I DO NOT. You are comparing cylinders to each other at points, such as the first pump and the 6th, not how high can we go with no pattern involved.
Lets assume #1 is lower, now you do a leak down test, which maybe a shop can do for you if you don’t have an air compressor and no rental tool leak down tester at auto zone??
All of this was free, next is to pay for a shop to use the scan tool to gather fuel trims, check for vacuum leaks due to bad fuel trims, this may also show a partially clogged fuel injector, they can do a leak down fuel injector test also, different leak down here.
Let us know what you find out, pull all spark plugs if easy, but don’t let the engine start while doing compression test, gas pedal all the way to floor also to let in more air.
You have swapped parts around so you know what you are doing, compression should show a weak cylinder next. More expensive tests can be done but lets wait to see what you get now.