Unstable during braking carbotech xp10/xp8

fryzia23

Did my first track day last weekend on a proper race pads. I went with recommended xp10 fronts and xp8 at the rear for track days. Also have front z1 2 piece slotted rotors and stoptech sport rotors at the rear also slotted. Ever since changed to this setup, the car is very unstable during hard braking. I could feel it the first time I tried them during bedding on the street. It almost feels like the rear wants to step out in either direction. The bite is superb but I had to back off during braking because I totally lost confidence that I can keep it under control. For non track days I use nismo pads all around and do not get that sensation under hard braking whatsoever. The car stays and behaves as it should. I tried to search but could not find anyone else with similar issue. Is it possible that the brake bias is too much up front due mixed pads? My next step is to try same compound all around instead going step lower in the rear. Just not sure whether to go with xp10 or xp8. Any feedback is very welcome.
My current setup:
Front brakes air cooling ducts
Stock nismo shocks with swift springs
Front and rear whiteline swaybars
2.5 neg camber with zero toe up front, 1.5 neg camber with slight toe in at the rear
hankook rs3 275/305
os giken rear diff