DIV 1 rally/track suspension setup

[NoHachi]

If those are truly your springrates then there's your problem.. Extremely oversteer biased. You'll need one hell of a front sway bar to balance them out. But it would be better to add one kg/mm to the fronts and the sway bar.

As you probably know, if you are at equal freqs front-rear then you have no grip left in mid corner and corner exit to accelerate. Since there is still aero, tire and slip angle drag the car will start to decelerate.. Try to aim for at least 60% front roll bias.

I also seriously doubt that 4/4 is 1.9Hz. 1.9Hz is Lotus Elise territory and works very well on any asfalt. 1.8Hz saw an MX5 to sub 8min laps on the nordschleiffe.