power to manual problem. need advice!

i finally got my Dr.Diff manual master cyl mounted and bled,bled the whole system real good ,and i am still getting a soft pedal and nearly no brakes. i know the system is bled good,so could it be the proportioning valve? i done this on my old rockcrawling jeep and i didn't have any problem,i could slide 38's from 50 mph easily and straight. this damn thing wants too pull around and the rear wants to lock up more than the fronts,pointing towar the prop. valve. i figure someone on here has had to have done this before! thanks in advance!