Before you change everything check this.
I have been running my TC3 with the stock ball cups forever. I do notice that the cups on the rear will catch on the rim if the wheel is bent or if I am running wide foams. A wheel that is catching on the cup will make the car feel loose since it is locking that wheel up momentarily when cornering. If it pinches it enough it can pop it off the ball stud. Check your axles and drive hexes too and make sure they're not bent. You may have a bad hub bearing too.
Just my .02
Futaba, O.S. Engines, Tornado Fuel, Schumacher Racing, SpeedPassion USA, Eggroll Inc., Desoto Racing, Vesselli Racing