why does my 1150 make my converter stall more and better than my 1050

More torque is being made. The greater the amount of torque input into the converter, the higher the stall speed will be . Basicly it is more difficult for the converter to transfer the increased torque energy from one half of the converter to the other half. Converters are basicly viscous couplers.

An off the cuff theory is the fuel curve is better matched to the engine's demands with the 1150.