Occasional Rough Idle P015a, P015B, P0301
 

2018 BRZ tuned with a header and flex fuel kit. I've been running e85 exclusively since 2019.

In late September it started up with a rough idle one morning but drove fine otherwise, later that afternoon CEL came on while I was driving on the freeway. Checked the codes and I believe the 3 above were listed under pending, with only P015B and P015A under the stored codes. Cleared the codes and filled with 91 on the next tank. No CEL but occasional rough idle over the next weeks.

A couple days ago (now on my second tank of 91, no e85 since the first code) I was on the freeway again when the CEL turned on again. Car had a rough idle when I was at a light. Later on the drive back home the rough idle was gone, light still on.

Any ideas?