I have a 2003 hyundai tiburon gt 6cyl with 154,000 miles. It it doing something strange. When I first drive it for the day it shudders a bit and when I take off slowly cause I live in a quiet residential neighborhood the rpms go low and all the dummy lights on the dash come on and the car dies but it starts right back up. Also when im driving at regular speeds onthe road the rpms go up and move like normal but then they will surge up real fast and then go back to normal. I just had a brand new battery put in, new air filter and the mass airflow sensor was cleaned. What could be the problem?