I haven't experienced this personally. My car was on a custom dyno E85 flex fuel tune with ecutek for a while and there were a couple times I brought it into a

I haven't experienced this personally. My car was on a custom dyno E85 flex fuel tune with ecutek for a while and there were a couple times I brought it into a dealer. The only thing they noticed and cared about was the flex fuel kit, and even then that was because they mistook it for a custom aftermarket fuel pump, when in reality it just reroutes the fuel line through the sensor. In fact, about a year after this my warranty had expired. But Subaru ended up extending it due to COVID and offered to reimburse any repair expense up to like $500 or something. At that earlier time, dealer missed some issues despite running diagnostics on my ECU and wiring harness. So later I brought it to another shop that fixed the problem. Subaru still reimbursed the whole cost of that repair plus parts. This was after they would've checked my ECU and seen that it had been modified with an ecutek license.