In my opinion the Rostra - it's electronic not vacuum operated. I installed it several years ago on my 97 Tourer and it's been reliable. Not trivial to install but worth it I think. I paid about $500 for the kit IIRC. It was complete though I did buy extra magnets. Still having a problem with them occasionally getting flung off the front wheel brake rotor - JB weld surprisingly can fail with the centrifugal force and road shock. It still works even if several magnets are missing. On a new install now I would probably find another place like inside the rear wheel "drum" left side so they wouldn't fling off easy. Writeup at
http://www.valkyrieforum.com/bbs/index.php/topic,86066.0.htmlIf you mean a throttle lock the best by far is a Brake Away. Spendy at around $190 but it's well engineered and executed out of aircraft grade aluminum. Looks good too. I put one on 3 of my Valks and the Magna.