Whats the best way to launch a S4 with stock clutch and just ECU?

Safer to strap a "JATO" to it;-)

push in clutch, full throttle redline, drop the clutch
 

dont actually do that.

Need to master the "Side step";-)

bypass the N249 and launch under boost

i hold rpm around 3500-4000rpm until the light is about to go green the give it gas
 

and the let out clutch quick but smooth but quick.. usually ends up around 4500rpm when this is done..