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Owns A Torsen
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Misses are usually caused by one of 3 basic things, spark/fuel/compression. Usually may I add.
The firing order doesn't change so if it started missing before you changed anything you should be good.
That 4 banger is easy to manage. Since you are familiar with the spark plugs, borrow/rent/buy a compression checker. Pull the supply wire to the coil packs so you have no chance of starting and measure the compression in all 4 cylinders.
People may have different opinions but in mine it is more beneficial to have all cylinders be within a certain percentage of each other than having ultra high new engine compression.
If they are that is not your miss.
The rear oxygen sensor will make no difference it is only used to tell if the cat is doing its job. The first one (upstream) is the important one.
Next I would check injectors. If your scanner has spotted one particular cylinder, the easiest thing would be to switch the injector between a cyl that is firing good and the misfiring one. Reset the code, start it back up for a while see if the cylinder misfire moves also. If it moves then replace that injector. If you lived in Ohio I would hand you a few :)
Start there, the problem usually rears its ugly head during these diagnostics. Please report back your findings for the benefit of all!
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