I would guess that your slipper/dif is lose and that is why your not getting good power to the front. As for springs the stock dual rate springs are garbage. the open part is to soft and the tight parts and to hard, not sure how easy it is to find Losi parts in norway but thier springs are great and come in many strengths. You want 3.5 inch for the rear and 3 inch in the back. I run 3 pound springs in back and 1.5 pound springs in the rear and that works well for me I don't race though.
your wheel hubs might be stripped in the front and your shock oil is shot so you will need to replace that and get bigger springs if you want to make it last longer