1600in/lbs =133ft/lbs max/"peak". Were you watching videos of impact DRIVERS or impact WRENCHES? If a lugnut is properly torqued to 100ft/lbs (this changes on the type of vehicle), after some driving I wouldn't expect less than 200ft/lbs to break it free. Cordless impact WRENCHES are upwards of 400+ ft/lbs of torque.
I don't know of an impact driver that I would expect to be able to remove properly torqued lugnuts, even a minute after they were installed. If you hammer on a lugnut for a minute one may come loose but the last one will be the toughest.
I haven't had much luck using 18V impact drivers on many screws. It is difficult to find a strong screw that won't break from the torque of the 18V impacts. 12V seems find, or an 18V drill/driver. Larger bolts/screws work fine.
Damn, a day late an a buck short....