I was gonna recommend the a-j controller, but his website is down.
.
Look over at sh.org for more info Shen.
It's basically a controller that is set for a gear you want it to spray in, and once it sees 100% throttle it will richen the fuel system. When you have it disengaged or not at 100%, the bike will run like stock.
Can be used with a PC.
You may also want to check with Daniel (Goldenchild) He has started selling nitrous parts also.