Midway Automotive & Muffler

I called Midway Automotive to ask how much it would cost to put in a new clutch for my 2015 Mustang GT. They said $1100, so I brought it in on 9/29/2022. I said I wanted a performance clutch and they said it was no problem. Later that day, the desk manager called me and said they were going to put in an OEM performance clutch, but it would cost $1600, maybe more if they had to fix the flywheel. He said he'd call me back. I said okay. He didn't call back until the next day, when he said it was done and I could come pick it up. I left and immediately noticed the car was making a loud fluttering sound and losing power. I brought it back and told them what was happening. Pat, the owner, had an employee ride with me to see what was going on. He heard the same thing and put it back on the lift. He said there was nothing they could do because they didn't cause the damage to my exhaust system (which was a lie). He said if I wanted it fixed, I'd have to make another appointment for the following Tuesday. I said no, I didn't want to drive it around and cause more damage. He denied responsibility and told me not to come back. I found where they tried to spot weld the damage to cover it up. Their mistake caused my car to misfire and it still isn't okay to drive. I'm very unhappy and stuck with these problems. It will cost $1600 to fix the damage they caused. They deny responsibility and I don't know what to do.