I remember reading a DIY article on how to make your own dual stage switch on the old Greddy Profec B boost controller.

I've search but can't find anything!!

 

all ya had to do was type : profec switch
in the search ...c'mon maing!! haha j/p

https://honda-tech.com/zerothread?id=649401
http://home.insightbb.com/~niedejb/switch2.html

hope that helps,
mike

 

all u need is a stereo plug, some wire and a switch. when the corresponding wires are connected, they return a small voltage back into the profec unit which switches between hi and lo boost modes. there's definitely a long post on it way back that i participated in. try the old archives. good luck