I put a switch in for my amal valve, i have a stg1 chipped 2wd sapphire, it worked but soon found that i ran it full boost most of the time anyway so no need, just didnt put my foot down so much. Also found it a touch annoying when being beat of the line to have to flick the switch, a couple of times when i flicked the switch i had to hold on to her one handed, looking down at the switch, not much fun really