I've gotta get my car dyno tuned this spring, since I put my MS3 in over winter. My nitrous went on after that, so i've never sprayed before.

Should I get my car tuned for the MS3, and then come back at another date to get it tuned for the nitrous? That way I can make sure everything is okay, start out with a smaller shot first before i jump to the 150?

Or just do it all at once?

 

do it all at once. if your tuner is good he will tune the cam and then from that it should be just a little tweeking for the spray.

 

i'm just nervous to have my first spray right on the dyno..., and then having to jet up, etc etc

 

do it all first time on the dyno - i jumped the gun with throwing my H/C together without keeping fueling need in mind for N2O, ended up needing to get it tuned for NA power up front and wait on installing my fuel pump and going back to get it tuned for N2O - it just costs more money that way
your tuner can monitor everything (both NA and on the spray) while on the dyno and make sure everything is safe & that you're getting the most out of your setup