Go to the Motorsports menu
Change "Anytrim mode" under Anytrim3 to spark corr
Change "Input control source" under Anytrim3 to "Speed 1 input" (or Speed 2 input if that's what you want)
Go to Motorsports -> Anytrim3 Curve and make it what you want based on road speed.
That's about as close as I can come to a 1st gear ignition adjustment at the moment.