I was going to suggest the RPM sensor but I think that's what you are calling the flywheel sensor? Are you absolutely sure the timing is out? Given all the checks you have done and the fact that the car acts up when under load (kickdown and passing) I would suspect a fuel related problem. Something as simple as the fuel filter or dirty injectors. Both these problems won't create fault codes. Start thinking fuel problem instead of ignition problem. My two cents....