2010 LT w/ sudden bad misfires, rough idle and bucking in low gears

Adaviswells

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Hi everyone, I'm new to this forum and hoping someone here might have some insight on my vehicle's issues. I'm at my wits end and starting to panic.

I've got a 2010 LT, 2.2L ecotech barely over 100k.
- CEL on with codes for cylinder 3 misfire and low voltage knock sensor (not stressing that one so much).
-severe, shaking/jarring misfire at low speeds only with flashing CEL.
- Rough idle especially in reverse (almost to the point of stalling, but that level of severity is only sporadic).
-Occasional bucking when shifting (automatic transmission)in low gears only or from park/reverse into drive.
-MPG had dropped very noticeably.

The misfire code would come and go for almost a year with no change in the car. 6 months ago the weird bucking began, but it also went away for a couple of months of the time as well. Very sporadic. The rough idle has slowly developed over the past 2-3 years and wasn't really super noticeable until recently (i bought it late 2013). Last week the violent, shaking misfire started along with a flashing CEL during. It returned to normal driving after less than 30 seconds after the misfire. It only occurs at very low speeds (last time was simply reversing down my driveway and idling really rough turned into a misfire. Other episodes at times like slowing to a stop at an intersection/accelerating after sitting at an intersection). This has occurred 5 times now and the car is parked until I can make heads or tails of this issue.
So far we've done the following:
- replaced all 4 coils
- replaced all four spark plugs
- clean MAF sensor
- done a simple upper engine cleaning/throttle body cleaning with seafoam
- put two bottles of seafoam into gasoline to run through and hopefully clean injectors somewhat, just in case.

I have looked all over the Internet and asked around I'm finding all sorts of different responses and possible problems, but I decided to ask about my exact issues and hope for better responses. Anyone have even a vague idea what could be going on? Car most likely going into shop next week if I can afford it. I lost my job, so I'm on a bit thin ice money-wise. Thank you in advance!!!
 
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