I recentley installed a nitrous works adjustable kit to my 89 325is and I love the resuslts-The kit is adjustable from 40 to 75 horsepower and installs just like the previus reply-My kit came with a thrttle switch witch I chose not to use because I wanted a little more control than this-What I did was get a 2nd hazard switch and had the face rescreened to say NOS-I then installed the switch above my radio in a blank spot-then using relays I rewired my horn so that when off the horn works as normal and then when you hit the switch over the radio-it turns the nitrous on and turns my horn button into my activation switch-now when needed-I just hit the switch and hold down my horn button as long as needed to induce the nitrous-hit the switch and I then Have my horn back and nitrous disabled! I enjoy this because I have full control and if there is a problem I can simply shut down the whole system with the push of a button! Phil