Help me identify this missing sensor please
 

1995 4Runner, 3.0 with rear heat option

Doing a head gasket job and I've got it torn all the way down. I want to replace the hoses and whatnot on this aluminum block (water bypass?) at the backside of the engine. If I'm wrong on the name of it, and you know the correct name of this block, please share that info lol. When I got it all torn down I noticed this part looked like a sensor that had been broken off at some point in the past. I'm generally pretty careful when disassembling things so I'm pretty sure I didn't break it. I did, however, break the vacuum switch next to it (already removed in the pic) and will be repairing it before reassembly. The one I'm asking about is at the red arrow. Forgive my mad Paint skills haha

Attachment 110607

Found it. Cold start injector timer. Pretty spendy part! I also looked back in my "before teardown pics" album and saw where the plug was zip tied to a coolant hose and not hooked to anything. Guess I missed that when I was taking it apart.