I'm 16 years old and live in Utah I believe I'm of legal age but I'm not sure. Any help would be much appreciated.

No you are not of any "legal" age and you can only go to leave where the court order says. If you wish to live with the other parent, they will have to file for custody of you in court, The court will let you testify normally.

If your mom files for custody or to amend the order that gives
Custody to your father ( I am assuming he has custody)
If and when a judge hears this they may take your wishes into consideration but in Utah you are a minor and have no rights.

The main thing the court looks for is what would be best for the children, and their opinion may be quite different from yours.

There must have been a reason your father was granted custody in the first place and this could have still have a lot of influence with the court.

You could write a letter to the judge and tell them why you want to live with your mother, (if the case goes that far) that would probably be the best you can do.

You will be able to move out when you are 18 and considered an adult in most matters.

I also live in Utah and have been through a custody battle , hopefully your parents can work this out between them .

Have you talked to your father about moving in with mom?

And if so, what did he say?

You have 2 more years before you can be considered as an adult. Hopefully you can talk to both parents without necessarily going to the courts.