new stall acts like a stock converter

first thing i would do is put the trans in high(3rd) and put the parking brake on...

rev if with you foot on the brake till the engine no longer increases rpm...

that will tell you what the max stall of the converter is unless your tires start to spin...

now when you said it starts pulling around that range were you mashing on it or just taking off? these new converters are tighter down low then they used to be for better street maners, but jump on it an see what it flashes to...