that sounds like a lean surge. turn the idle mixture screws out 1 full turn. this will make idle too rich. but drive it and see if the surge gets better. if it does then you need a larger main jet. another way to check this is get a propane torch. take the tip off and put a long hose on it put the other end into the air cleaner drive the car and try to tune the surge out using the valve on the torch these 2 methods have worked for me many times.....ted