Powderchowder I put nos on my 4 stroke last year and love it. The new Bossnoss system from Boss is what I am using, and it is completely regulated so and you add add noss it increases your fuel, reducing or elimiating melt downs. I went with a 40hp shot it works great, my Rpm goes up about 400-500rpms and stays there until I let off. With the regulated system you can hold the button down until the bottle is empty if you want!!
I find with my sled when you let off it bogs from a second or two, from it try to burnoff the extra fuel that just went into the cards. I was told by Bossnoss if you go any higher then 50hp you have to start mixing with race fuel. Good luck and let me know what you go with.