niznai

I would check that all wheels are spinning free. I have seen a lot of people "pinch" the bearings with the wheel nut. Personally I use a spacer between the bearings (inside the carrier) to avoid this very problem.

Sounds like you have a bad case of "liftoff oversteer" a very well known problem of all FWD cars (even real ones). Tires are a significant part of the equation, weight distribution and transfer another.

A quick check (after you checked the wheels are free spinning) is to use (if you have) a NiCd or Nimh battery (or load your Lipo to equivalent weight). The weight difference might be the ticket. If the car behaves then, you know where the problem is and can address it then.

Too soft a front shock and damper might allow too much weight transfer too as can too much rear droop. A combination of all to the most undesired effect is of course quite possible.

If you don't want to buy tires, find someone who can lend you a set of Hpi cross x pattern radials and run them on good, clean tarmac until they are warmed up. If your car is still tete-a-queueing under braking with those, you've got to work on your setup.