I've noticed it misses or stutters under average throttle. At idle it's fine, and at WOT it builds boost fine and pulls good with no issues. But when accelerating normally it stutters. Not sure if I made that clear, but it's a weird symptom. The check engine light is on, so mechanic ran a scan and said it was a rear O2 sensor but didn't think it would cause that issue. I don't remember the code. Anyone else have this issue? BTW it's 2.7T/auto.