I'm going with a MSD digital window switch, so I can still spray in first, with the car hopefully halfway hooked by then... Actually, at 3400 RPMS and WOT, if I don't have some semblance of traction, it's time to start changing the suspension, lol. Also, 90% of purge kits come with a button, so I wouldn't worry about that. What I WOULD do is hide a "master" power switch somewhere... don't want valets finding the "happy button".
