Do an on-line search for "What causes surging in car engines?" by Richard Rowe. In modern computer controlled vehicles, if there are fuel problems or other problems the computer is jockeying back and forth, trying to get the optimum parameters, and cant because of malfunctions like clogged filters, leaks or sensors that are going bad. This and other writers may offer suggestions that you have missed in your replacement of parts that did not help. Let us know how you solved the problem.