weak direction

[teles]

Hello, I have one xxx-4 g+ (stock) at a little time, and do not manage to tune the car to have a firm direction in tracks of hard clay , it always extends the curves , on and off power.
The MIP are already in the limit , the battery is the front, the arms are leveled, the servo is a Futaba 3305 and it protected by a Kimbrough Gas Car/Truck Servo Saver , the tires was SCHUMACHER MINI PIN ,maybe were not the indicated ones, but there were other cars with the same tires and they did much better .

I must test oils , toe´s , camber's , springs ???
Someone has some trick or hint, please ...

All the suggestions will be accepted, owners of xxx-4 better

Again thanked