Pat;
Bob Szabo wrote a FANTASTIC book about mechanical injection.
www.racecarbook.com
The book even covers the topic you're asking about.
The answer is yes, you can use a 2-step... Getting the correct a/f ratio however will require some testing. More than likely you'll also want a electronically activated lean out to work in conjunction with the 2-step.
This will allow you to tune the a/f ratio when your foot is on the floor with the 2-step is activated.
The other thing you can do (probably more expensive), is to use a pneumatic cylinder in conjunction with the 2-step. The air cylinder will be used to control how far the butterflies open which again will allow you to adjust the a/f ratio at which you launch at.
Hope this helps....