Have you pulled the code? Each instance that I have seen a blinking CEL, it was a misfire, which would explain the power loss.
I agree, and the change in A/F ratio could be the result of an issue rather than the cause. The commanded A/F changes constantly with load and other factors so unless you are datalogging the car for tuning purposes there isn't really a reason to watch it.
If your check engine light comes on your only option is to have it properly diagnosed at the dealer because we can't do anything for you.