I'm no expert at all but don't think it's your imagination. Take a look at the tread on the E3 compared to the Met.
I'm had E3's on 3 different bikes and got really good wear out of them but once the even start to wear they howl big time. On the positive side, because of the tread pattern on the E3, they don't tend to get caught up in the tar snakes or grated bridges which is nice.
I suspect the imbalance that you're feeling is because the E3 is going where pointed and the other tire is tending to follow irregularities in the road.
Just a thought and good luck. My opinion may be worth
Greg:hurts: