IMHO, after spending so much money and the car is bad again, go to a reputable dealer and have them figure out what is wrong with it now. You've been to the other mechanics. You've spent a lot of money. Go to a dealer. You'll then have someone to complain to if they mess it up. Really.
I've spent SO many thousands on my stupid Ranger. There are two people I would have work on the ranger other than a dealer. Sadly I'm never by either one of them.
There are good independent mechanics. I just don't seem to find them easily. You seem to have the same problem. I hope you get your car fixed.