My 07 edge fwd starts to shake/shudder around 40-45 mph. I replaced the tires and had 2 different places balance them and it still shudders? It's kinda wired because once I start to feel it I can mesh the gas pedal down a little and it goes away until I let off the pedal it starts again, also I can do a slight turn right or left down the road and it goes away? Any thoughts would help!