One of my references pulled a similar scenario. What solution: I looked at another recommendation letter that a reference had sent to me for review (ie. he was asking if I thought he should be boasting about anything else). After getting the idea of how he wrote it, I more or less changed the writing style, facts and accolades and passed it over to the reference for review. He thought it looked great.
Keep in mind, you MUST give yourself a pat on the back. I've had a reference that sent a letter exactly like I gave it to him without adding anything in. So DON'T be modest. Fact is, if your reference doesn't agree with you on a statement he/she will confront you about it, which gives you an opportunity to justify why I included said statement.
My pointers:
- Keep it factual
- Make yourself look like an applicant that you would want to admit if you were in the admissions committee.