does anybody have it without other GTSpec braces to help me?

my rear end seems to travel by itself during the speed highway turns. I have stock g35x soft suspension with the RWD rear swaybar and GTSpec front strut bar

when i start to make a 45^ degree turn, doing 90 mph my rear end begin to bounce from side to side and I cannot go higher speed and keep the car stable!

how do you think, will this 6-point brace help me or should I buy hotchkis awd swaybars instead?

 

You shouldn't make 45 degree turns at 90 mph in a road car. There's your problem.

I have it. It won't really help what you describe much, that's not what it's designed for. The sway bars will help much more. Particularly the front one. You shouldn't use the rear sway without the front. It's making your car more prone to oversteer which is what you're describing. Simply taking the rear sway bar off and putting it back to stock will help.

 

Just having fun on the track

my front is tightened by the gtspec front strut tower brace and strong fiberglass underbody, so in general, i don't have oversteer...