Engine misfiring even after repairs... PLEASE HELP

2017 Tacoma TRD Pro w/ ~230k miles. Vehicle has been intermittently misfiring over the last month/month and a half (only under heavy acceleration). I cannot figure out what is causing these misfires... I've listed a breakdown of the timing of the misfires, along with their associated repairs, below. Please help me out here because I am throwing a lot of money into this truck and nothing seems to be fixing the issue

5/2: Cylinder 3 misfire P0303 occurred while driving over the Santa Cruz Mountains, and vehicle subsequently went into limp mode. After cycling the ignition, the problem seemed to go away and normal operation continues. However, after heavy acceleration, cylinder 3 misfire occurs again.

5/3 - 5/6: Vehicle taken to Toscalito Service in SF. DTCs populated are P0303 & P160500. Shop replaced all spark plugs & ignition coils (shop replaced all old coils with Denso 673-1311 coils).

5/7: While driving from SF to Reno (this time gaining elevation as I drove over Donner Pass), cylinder 3 misfire P0303 happens again, and vehicle subsequently goes into limp mode. After cycling ignition, the problem seemed to go away and normal operation continues. However, after heavy acceleration, cylinder 3 misfire occurred again. Thinking the misfiring may be a result of a loose connection between the ignition coil on cylinder 3 and its corresponding wiring hardness, I tried troubleshooting this myself by disconnecting and then reconnecting the wiring harness to the ignition coil. I cleared the codes and the misfiring stopped altogether. Tested vehicle under heavy acceleration, and no misfire occurred.

5/7 - 6/10: Vehicle operating normally. No misfires occur in this time frame (even under heavy acceleration).

6/11: Driving from Stockton to SF, cylinder 3 misfire P0303 occurs while going up in elevation over the Altamonte Pass. Vehicle subsequently goes into limp mode. After cycling the ignition, the problem seemed to go away and normal operation continues. However, after heavy acceleration, cylinder 3 misfire occurs again. Drove to the nearest Toyota Service Center in Livermore. After running the diagnostic, they could not identify the true source of the misfire. They said that the wiring, fuel injectors, ignition coils, and spark plugs all looked fine. That there were no vacuum leaks or malfunctioning sensors. They suggested that the source of the misfire could be a result of the aftermarket head unit system that I had installed in the truck (this was installed in January 2020). Their theory was that the electrical system from the head unit, while connected to the vehicle's factory electrical, could be causing a short circuit. They said they saw this on another vehicle they worked on previously, and that the misfiring had stopped after the owner uninstalled their aftermarket head unit system. After driving the vehicle home, I uninstalled my own aftermarket head unit system in hopes that this would resolve the issue.

6/13: Cylinder 3 misfire P0303 happens again while driving over Bay Bridge, and vehicle subsequently goes into limp mode. After cycling ignition, the problem seemed to go away and normal operation continues. However, after heavy acceleration, cylinder 3 misfire occurred again.

6/14: Vehicle taken to Toyota Service Center in SF and found the following DTCs (P030027, P030085, P030300, P160500). Shop replaced cylinder 3 coil pack with new coil pack (part #90919-A2008) and suggested that the coil pack installed by the shop I had brought the vehicle to on 5/3 was faulty. After replacing cylinder 3 coil pack, Toyota Service Center performed road test under heavy load/acceleration and observed misfire count. Verified after road test that no misfire is present and normal engine operations occurs, and verified no DTCs populate in engine ECU.

6/16: Engine misfire occurs again while driving over Bay Bridge, and vehicle subsequently goes into limp mode. After cycling ignition, the problem seemed to go away and normal operation continues. However, after heavy acceleration, cylinder 3 misfire occurred again.

 

Back in the day when I was a Toyota mechanic. When something like this popped up. First thing I did always was go and check each and every grounding point. A loose ground can cause havoc at times.

 

Remove your intake manifold and shake it. Maybe the variable runner valve came apart. Seems somewhat common from cruising this forum.

or run a borescope down cylinder 3

 

https://www.tacomaworld.com/threads...ld-flap-failure-2gr-fks-second-update.793953/