There is no such thing as "NGUI colliders".
NGUI events are sent to any and all colliders, provided the event mask matches. NGUI already does raycasting for you and handles all mouse and touch events. You don't need to do it yourself.
Get rid of your touch manager system. It's unnecessary.
if i read this right could you not just simple use 1 << 8, to change what layer the hit responds to, and just change this, works for me.