[DoomedE90]

I bought an e90 N55 335xi this year and I kept my daily. About a month ago I was fueling and I put 87 in it instead of what it’s tuned for (93)- without thinking that it's NOT the daily!!

The car started misfiring a bit. I could hear it burping clearly. Fast forward and talking to the guy that tuned it (stage 2+) on what I should do, he recommended I refuel it with E85 when I get to half tank. Then run that tank and all should be good. So, I put in 4 gallons of E85 and then topped it off with 93 (came to be another 4 gallons to top it off). The misfiring got worse the more I drove it and the engine light finally came up, misfire on cylinder 6.

We drained the tank and put new sparks. I drove it for over 100 miles and the car still misfires.

We pulled out the fuel injectors and the one in cylinder 6 was missing it’s O-ring. It is worth mentioning that when we took the injectors out we were surprised that "Mr Trusted Mechanic" (the guy that tuned it) did not install the decoupling elements when he replaced the injectors last year (2023)!!

We borescope it and nothing was inside the cylinder so we just replaced all injectors in hopes that everything will go good. The car still misfires, same code after less than 10 miles!! What should I do?

I just cannot wrap my head around these questions:
1- How did the car run for a little while when the injectors were installed with no decouplers with no issues?
2- How would the wrong fuel cause much more damage than the injectors sitting inboard?
3- Where did the O-Ring disappear?
4- What could be the issue now? I replaced all injectors but it is still misfiring!