i ran 4 auxillary injectors on my turbo r/t neon back in the day ... right behind the primaries ... controlled by a home built megasquirt and tuned with a aem wideband.

worked well.

i've run single injector aux on a later build... this works well under boost as long as you have a intake manifold that distributes air well ... i imagine the crossfires manifold is more than adaquate.