So far I am loving the changes. TCU: The shifts are smooth and fast up and much earlier downshift points. The TCU upgrade is critical as it allows the transmission to match with the APR map. I think the pair is a must and should be considered mandatory. ECU: This is a great motor and APR makes it better in every way. Power is delivered quicker and with greater force, especially when the throttle is over 50% down. The engine winds up fast and triple digit speeds are there in a flash. Passing power will suck you into your sport seats!
If you like your S3 but want to see what 357HP and 366TQ feels like, I recommend it.