how do they? what exactly what do they doshould i use one one with a dry kit

 

It turns the nitrous n at a certain set RPM and shuts it off at a certain set RPM, thus the nitrous is only spraying in a window of RPMs that are set by you.

Usually people start off with the on setting at 3000 rpm's and the off setting at 100 rpms or so before their shift points or rev limiters.

Some people with auto cars use them so they do not have to spray through their shift. The most inportant aspect of the device (IMO) is that your not spraying if you hit the rev limiter due to a miss-shift or trans slip.

Either way, if you get one, I can help you out with questions, I don't live that far from you, so I can show you how it's wired if needed as well. Instructions are pretty good with the digital one, so you should be ok.

 

JBourne is correct. Since you're a M6 it would be a very good idea to get one. One missshift and you could have trouble.