Carrier/rack problems of the 2016 Buick Enclave

My car was repaired by a dealership in texas. First they said it was a fuel injector. They replaced that. Then they said that that didn't work so they said I had a cracked head. They replaced that. I brought it home to shreveport, la. And it had gas fumes coming of of the a/c vents. The dealership here in bossier city that they put in a broken part. They supposedly fixed the problem. I picked the car up and it still had gas fumes. I took it back. They smelled it. Kept it for 2 days. They couldn't find the problem so the kept driving it and running it until they couldn't smell it any longer. I picked it up again and I still smell it. I brought it back but they are denying that they do. Even lied to gm customer service that they rode around with me. I had a horrible headache when I returned home with the car. It's been parked for over a week. I am terrified to drive it scared it will catch on fire or my children and I will get sick. Please help me. I have tried working with gm but they are no help. They give me the run around. The mechanics have also lied so many times regarding my car to gm customer service. I need someone in my corner. I haven't been able the drive my car sine 5/16/2019. It went to the 1st dealership on 5/18/2019. I drove about a total of 1. 5 since.