All it takes is just the right amount of pressure to change the throttle position input to the PCM & TCM enough to compare it to the engine load and decide if a single gear (or multiple) change and/or change in lockup status is necessary; also for the computer to comply with your engine speed change. The NAG1 is all about this (I imagine the 8sp is as well), especially on hills or maintaining exact cruise control speed. A change in pedal position can cause shifts to happen, but it's still a function of kick down, even at slower speeds. You don't have to romp on it, does NOT require a full throttle stomp. My '72 Road Runner with a 727 3sp did it (granted there were only two gears to choose from). This really isn't anything new, it's not like you're exerting actual shift control (like with autostick or paddles) over the transmission, you're just causing it to downshift. I imagine once you're done playing footsie with the gas pedal it settles right back down to the gear it was in for the speed you had it at (if you return to that speed). All that tapping does is trick the TCM into thinking more pedal position is being applied and needs that gear change. It's not a special feature lol.
