Hello Good Sir, 

   I hope this question finds you well, this morning. 

I have a 2011 Avalanche 5.3 with 205k miles. Automatic. Has functional AFM. 

Under hard acceleration, from appx 15mph to 40 mph, the engine went from doing its thing to a sudden loss of power and back firing. It really sounded quite similar to a clogged catalytic converter but I can be fairly certain that isn't the case, as they were just replaced. Although I was still having some misfire issues that were never resolved in cyl 4. The misfire count has since gone up. 

P0060

P0300

P0455

P2270

P0134

U0140

C0561

Stabilitrak error on the dash, and I think I saw traction control off too. Had a low voltage deal pop up regarding the battery even though it is still doing its job well. It is from 2022. 

Plugs and tps were changed 20k miles ago. Fuel pump is doing well. Battery is good. Grounds appear to be fine. Wiring does not appear to be broken anywhere. Did have a fouled plug in cyl 4, took it out and cleaned it, but haven't gotten to the store for a replacement yet. Havent swapped a coil from another cyl just yet but am about to. Would love some insight on this, as I have already taken three days off work this week which basically ruined my pto for a vacation... Im gettin a little flustered with it. Thanks so much for your help, I certainly appreciate you for it!