Why does my car on rain starts to understeer WAY to much?

[visual delta]

Recently i bought csp preview and I activated the extended physics in order to get real physics with rain, and it worked fine, bur recently I try it on a gt3 and a S15 and when I change with sol planner or the rain begins, my car just understeers like crazy, i even change like medium and esay or real in the sol planner for the rain physics but in any gives me a lit of bit of a result, any solution out there?

I have tried rain tyres and its the same, also when this happends the throttle just goes crazy, im at gas to the metal and the revs are like laggy, with or without traction control

[tame plank]

This is jut a matter of bad mod quality

[visual delta]

But how if this is csp preview with sol?