Nitrous is not a problem on a single Vanos BMW 4.4i engine provided the normal precautions are taken. There's a couple of documented installs in the Roadfly E39 forum (http://bimmer.roadfly.com/bmw/forums/e39/). Do a search on Nitrous Oxide and you'll find "JimLev" who has a 75 shot wet system on a '00 540i 6-speed. Looking at his posts, his install dates back to '02 or '03, so he's gotten some longevity out of it. He started out with a single dry 50 shot, went to a dual action 50/50 shot, then converted to a wet progressive system. Here's a picture of his install:



I've run N2O on Supra MK4. It was fun while it lasted, it was just too much to worry about, especially when other people were driving my car. I blew the engine, probably hastened somewhat by the N20, but it was tracked heavily, so it was inevitable.

I would not install a NOS system on a high mileage 4.4 engine. And you might want to kill the rev-limiter. But heck yeah, it's doable. I didn't think it was practical until I read of Jim's experiences.