****UPDATE****
Here are some hard numbers showing the improvement since the professional driving instruction (all times are from Willow Springs Big Track and no changes were made to the car during this time);
December, 2011: 1:45 (min:sec)
February, 2012: 1:44
This is where I felt that I had plateaued and wasn't getting any faster on my own so I had the professional instruction in March and...
April, 2012: 1:40
One day of professional instruction took 4 sec's off my lap time! 