grand jury subpoena

What is the name of your state (only U.S. law)?
Massachusetts
I have been subpoenaed by the grand jury to testify in an insurance fraud case against my car repair shop owner's who are my friends. I do not want to testify against them. Can I plead the fifth? would there be any repercussions for me if I do so?

You can't "plead the 5th" because that only protects you from SELF incrimination. You must testify and you must tell the truth.