ET difference from 3.91s to 3.54s

How many cubic inches are you running? I'm running 3.23's in my car, some day I'll try more gear at the track but I love these 3.23's on the street. It runs mid 10's but it is a mild 500" big block.
Mine is 360 cubic inch small block. If you are running mid 10s with 3.23s that is awesome! I hope to run mid 10s with this small block once the pro charger is installed.