I hope this does not come across as disrespectful.
It is real easy to fall into the trap of "shotgun troubleshooting." This is what I call it when you just start throwing parts at the problem.
In about 99 out of 100 situations like yours, you would be money and frustration level ahead by taking the car to a competent and properly equipped troubleshooter and PAY him to diagnose and repair.
This is especially true for a car with expensive parts such as this.
I realize that it is sometimes difficult to find a competent troubleshooter, but I expect that in your case you would have saved money even at dealership labor rates.