16Skyline : Check your ESC programming for Drag Brake and Minimum Brake. Assuming you are using GTB ESC, there is a program to limit the amount of drag braking off throttle. Read your ESC manual.
I use program #1 for drag brake & minimum brake. Program number #1 is the softest value for braking.
Secondly, you may try one or two of the following :
1. add more droop effect in rear ( using hudy block, use lower downstop value at rear ),
2. use harder spring at front.
3. use less droop effect at front ( using hudy block, use higher downstop value at front ).