I really don't like the slotted rotors myself. They burn threw pads b/c they slice a layer when they go around. So i would get some really good cross drilled ... probably cryo treated
i'd just stick to some regular flat rotors. unless you are going to be rippin on the track all the time there really is no need for drilled/slotted rotors. like said above it can reduce braking due to less surface area. maybe just do the cobra upgrade and see how that goes.
if you're still not satisfied throw in some steel braided brake lines and see how that feels. should stiffen up the pedal abit.
It could be anything from dirty calipers to worn out rotors that are too thin and there isn't enough to grab onto even with new pads. Your brake lines may also need flushed out cause brake fluid does go bad,
