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If you clear the codes does the P0171 code come back right away? Are you still getting the cylinder misfire codes?
Remove the intake boot from the throttle body and with the key in the on position have somebody depress the accelerator pedal does the throttle plate inside the throttle bore move at all? If they push the accelerator pedal clear to the floor will the throttle valve open completely?
Does the throttle plate even try to open or does it only open slightly when you depress the accelerator pedal? Did you replace the whole throttle body assembly and accelerator pedal assembly with a new or used parts?
Did you check or replace the ETCS fuse in the fuse box under the hood to make sure that it was not blown? As I recall it is a 10 AMP fuse. This is a main power supply for the throttle motor.
Did you try and swap the ignition coils to the two middle cylinders and also the spark plugs to see if the misfire continues to those cylinders? If the vehicle is not been running long enough it may take some time for to set the cylinder misfire codes in the computer.
If you take these two components out of your car and put them back into the other known working vehicle does it accelerate and open normally on the throttle? Have you checked the voltage swing on the sensors when both connectors are plugged in on the vehicle?
You have a manual that shows you the pins that you need to resistance check on the components themselves?
I submitted a phone consultation offer to you to discuss this matter in more detail if the components all work on the other vehicle and do not work on your vehicle and vice versa the bad components on the known good car than the problem is in the wiring this will get complicated very quickly. I can walk you through some voltage test but that would be difficult to do in this type of format. Let me know how you'd like to proceed.
There are a couple of quick things that you can check as far as the wiring and those are the ground circuits for the engine control computer and the sensors. If they are corroded or screwed up they can cause all kinds of crazy things to happen. Click the attached link in the illustration the ground connection EH is difficult to get to its under the intake manifold towards the driver side. In most cases you have to remove the intake manifold to check and clean that however some guys can get their hands in there and get the bolt off without pulling the intake. ground point EG is located on the left side of the cylinder head and his visibly accessible make sure the wires are cracked going to either of these and there's no corrosion.