Well just as the subject states is it? or is it a waste of money?
flip the switch around 3500+ rpms in first gear and let er rip
waste of money for you
not needed, but doesnt hurt, especially if you are running a big enough shot to need to worry about traction, personally I would rather be able to arm the nitrous, purge the lines, and line up with all stuff ready to spray rather than, have to worry about flipping a switch after i launch.
http://www.aplusperformance.com
http://www.modified-motorsports.com
not necessary at all. the auto shifts well before the rev limiter so even if some slipping occurred, it would have some room for error or atleast give you time to backpedal the throttle.
for launching, you dont need to turn the arming switch on or have a window switch. learn how to control your throttle off the line instead of instinctively punching it to the floor. only go about 85% throttle off the launch and the first 20 or 30 feet before going w0t. it takes some practice to get the feel for the throttle position right before the nitrous engages.