I lied about why I left my job
Why did you lie about why you left your job, was it a financial thing?
No, I just didn't think that the job was very exciting.
You shouldn't feel the need to lie about why you left your job. It's better to be honest and any prospective employers will much prefer that you're honest with them. If you lie in your interviews, you probably won't get the job.
I did not want to be rude to my former employers.
They would appreciate the honesty more than you would hurt their feelings. They can use your feedback for the future.