I know what you mean. I thought I drove the wheels off my car at Suzuka for the MFR Cup but Im still almost 2 seconds off the fastest lap in my region. I can see 2 corners where I could gain maybe half a second if I nail them, but where the other second is suppose to come from, I have no idea. Its deflating that the top guys probably run my laptimes with 2-3 big mistakes. I dont have a ghost to run against, but in previous GTs when I did it seemed like these guys had a softer tire compound then me, its like their cars just gripped so much better. The reality is their driving technique is just superior to mine, and it helps their car grip the track better. Wish I knew what it was Im doing wrong
As for improving race pace, you need to practice your braking and turn in points until your comfortable with them, and they become automatic or second nature. Make sure you have your visual cues for braking points sorted. Also, learn to take it just a bit easier on more difficult turns that might cause you to spin or touch the wall. Push in the easy turns, but tip-toe just a bit in the difficult ones. That should help you make less mistakes.