But I don't think the 71 series II every came with a control valve from the factory. I see nothing in my FSM in fact I don't see anything related to water running through the intake at all. Now I'm getting concerned.

I was going to replace mine but couldn't find a replacement. Bought a "new" bypass pipe from MSA and the bend at the manifold end is to sharp so the pipes don't match up. Cleaned up the old nipple and am going to re-use the old bypass pipe. The new one has a different bracket as well, with a slot instead of a hole. I suppose one could make their own nipple ... if one could remove the old one. The one on my Z is frozen and I didn't want to take a chance breaking it, then having the nightmare of drilling it out and re-threading the hole.