This might sound weird but I suspect that may have been your problem. Some rubbers get pretty sticky during a run. Saucing them gets rid of that stickiness but if you were using the same fronts every run but only saucing part of them, they would still be really sticky on the unsauced portion making the car very loose. Try saucing the fronts completely but for less time than the rears. Sounds backwards but works for me.