brakes

im considering buying a truck, but it has a problem im trying to sort out before i run into a real costly problem, its a '90 b2200 cab plus bagged with flipped joints, its an automatic with power steering.problem is, he says,is when the steering wheel is at full lock or even almost full lock left or right, the brakes fail, at any ride height, he also says hes checked for pinched lines of which there were none, has anyone ran into this problem? buddy claims its the master cylinder, but i was under the impression your master cylinder either works, or it don't , regardless of steering. any input? oh, the description of the failure was, no pressure, pedal to the floor, and no decelerationthanks