you don't shoot c02 in your engine yuo shoot it in a metal piece around the air Intake or fuel rail to cool it down more... if you shot it in to your Intake you would just stall the engine
it's not called 'shots' though, i don't think. it's just called spraying carbon dioxide to cool everything down. or maybe i'm wrong but i've never heard it called 'shots' before.
in any case some people just use nitrous for both.