Sorry, self delete my post. TC is like a cluth for an auto tranny. Stall speed is like rpm and engagement. For example, you drive a stick and you release your cluth at 1600 rpm. What happen? The car would more forward slowly. Now, you rev your motor up to 2800 rpm and drop the clutch, your car would jump off the line, right? Well, the TC acts like a clutch. Higher stall speed is like launching at higher speed in a stick tranny.
That is why after market TC change to a higher stall speed.