I sent this post on your other post with this trouble and it's good you opened this post for help and this way more will see it...here's what I posted....
when you said it made a growling hum when it turned...are you saying when the engine turned or when you made a turn?...many years ago my EX.'s car wouldn't go much more then around 30mph and the problem was that the timing belt slipped a cog or two and that through the timing off so no power...I'd think the dealership would have checked all that and did they try driving up a hill...sounds like you may need to go to another dealership.
Hope others here will have some good advice for you.