I put the 03 cobra brakes on the front of my 99 GT. its got stainless lines and slotted and cross drilled rotors. I noticed that with a decent brake pedal applied, i get a shimmy/shutter that starts at about 40 mph and continues to about 30 mph. Its not serious just there a little bit. I don't get this if say i brake 35 down. Any ideas of what went wrong. Other than this the brakes are great. I can get on it fast at say 80 and i don't have this problem?!