Hmm Sammich you are just having the worst luck.
If I were in your shoes I would look into your states "lemon law". You may be entitled to a new sonic and if not now, will soon be at the rate your current dealer is going.
Failing that I would be checking out other dealers in the area, your current shop doesn't sound very lnowledgable. What they should do at this point, instead of just throwing parts at it, is put some "chassis ears" on the car and driving it around, and methodically pinpointing the actual source.
For those that don't know chassis ears is a diagnostic tool that has several, I'll call them microphones that are placed near the area where the noise is suspected to be coming from. Then the tech will have someone drive the car while they monitor which microphones are picking up the most noise. That would lead them to the problem area or get them closer to the problem so they can relocate the microphones closer to the source to further pinpointing the problem and eventually replacing it.
But not all shops have them, they are expensive and most shops can't justify the cost for how seldom they are used. So if you go to a dealer, find one that has them it may be the hot ticket to finally getting your car fixed.
best of luck to ya