I have 09 wrx. It was running fine on my e85 map. I switched to my 93oct map and noticed the problem. It was more from 2k rpm to 3k rpm, but really bad between 2.5 and 3k.
Talked to my tuner and sent him a log, he said it looked good. I decided to send him the map to see if something was wrong while i switched back to e85. He checked the map and said it looked good as well. Now i'm having problems while on my e85 map.
It's not as bad, but still noticeable. It feels like hesitation, or jerkyness from the car while slowly accelerating. It's not noticable when under wot. Initial thoughts were it might be the spark plugs, or fuel injectors. currently have dw 1000 injectors and 1 step colder plugs.
Any ideas? (or even suggestion for new plugs to try)