This is the nature of modding\testing our cars during lap days at the track. Some days your car is sorted completely and handles great and other days not so much. Which has been my case lately.
I would definitely speak to the technician who installed your rear brake pads. I would definitely inquire to the management how they can make it right with you. Maybe the next time you install rear brake pads they can do it for free??

 

Thanks guys.
Yes, tomorrow is about learning the track and honing the line. It will serve as a baseline for future trips to Mid-O.

Hopefully now my brakes will feel normal again. Lack of confidence in your ability to slow the car is not what we need. I will talk with my mechanic first chance I get.