No throttle-by-wire Harley will ever launch hard out of the hole with the stock programming from the factory. By design, the TBW ECU restricts the throttle position so that even if you have the throttle at 100%, the ECU will only deliver a preprogrammed amount (60-80%), if you are operating at 3k rpms or less. The only way around this is to use the ProTuner to override these settings and essentially set all throttle positions to 100% of whatever the operator has the throttle position set to at all rpms.
Only then will you eliminate that soft response you feel when trying to take off hard from a light. Nothing like big brother watching out for you (or perhaps trying to reduce warranty claims by reducing drivetrain shock from hard throttle starts).
The MoCo wouldn't want you hurting yourself or the bike by trying to do a burn out:)
I really don't think the MoCo does this to prevent folks from hurting themselves, they do it to prevent folks from trashing the el-cheapo parts. I don't think the new crankshaft likes sudden applications of significant torque at low rpm's, as it has a tendency to twist out of shape. Also tends to be hard on the new compensator design, and the marginal clutch. And lord knows that IDS sprocket with the little chunks of Chinese rubber wasn't designed to tolerate much of that abuse. And like previously noted, the new narrow belts may not like it much either. If someone wants to do lots of drag racing type launches with a recent issue Harley, I suggest they look for a leftover Destroyer or they rebuild the drivetrain of their street bike with some real heavy duty aftermarket parts.
Don't forget, Harley's are old folk's bikes and shouldn't be pushed very hard. If you really want to launch hard and impress your friends, get a crotch rocket.

BTW, I don't think the Springer Sinker posted about is equipped with Electronic Throttle Control.
Jerry