Want to improve lap times? Get a coach, someone who will show you how to drive the lines. Yeah sometimes we all think we are good but you'll be amazed at how much you really learn with a coach.
Buddy coaches at BIR. He coaches a guy who drives a stock Super Snake, within one yr he improved his lap time by 3 seconds and still improving. His son also improved his lap times by watching his fathers videos.
The car maybe fast, but doesn't mean the driver is fast.