Hi there, I have a 1999 Olds 88, 3.8 v6, which had the engine replaced with another good one. Previous owner did all the heavy work, but left a few wires to connect up. I have them all reconnected, but the 2 in the attached photos: First one is a hose connection, that comes off the power brake hose at the rear (firewall side) of the intake, marked with an "X". Second photo, is of a square 4 terminal female connector, part of a long harness. Any ID help on these, will be greatly appreciated.

connector, coming off a long harness at the back of the engine compartment

Why didn't he finish it up? Was the new engine out of the same year and make? Does it start and run OK? Your going to need to look around and find where the wire connector goes it it'* needed. Normally the power brake is straight to the intake. I have the info on that cat if we need it.

He didn't finish it, because he simply did not have time any longer due to being on the road (He'* an OTR road service mechanic,on call 24/7). Has not been started (I have to get fluids first) but was out of a low mile running vehicle,unsure of exact year. All my harness wires have plugged into the other engine sensors perfectly. The power brake hose is going to the intake as it should, just has that little nipple coming off the intake end of the hose.

An OTR guy does an engine swap. Where? On the side of the road.
You don't even know if it cranks?

#1 looks like it'* an accessory vacuum port. #2 maybe for an O2 sensor.

He did it in his shop, everything was correctly bolted down (I'm not a newbie when it comes to cars so I know what to look for) I also did a check, by rolling it over with a breaker bar,it is not stuck. Engine came from a reputable recycling yard, still had their inspection tags on it yet. All I really need is where the pictured wire goes, not questioned on why the guy I bought it from didn't finish it,
.

Update.... It is indeed an Oxygen sensor connector, for the one post catalytic converter. However, the converter was gone (like most are these days), can I run without it?

I would at least attempt to start it. Here'* some diagrams for you.
You'll notice here that your vacuum is very simplistic while that same engine in the Firebird or Camaro is much more involved. That'* why I asked what your new engine came out of.
Here'* yours


Here'* the Firebird/Camaro with the same engine. Might just need to plug that one.


Here are your electrical. That connector may go to something that'* not used on your platform although it sure looks like an O2 connector or purge valve.

I looked at the tag from the recycler, it came from a 2004 Impala

Also thanks for the diagrams, I'll study them. That plug is indeed an 02 sensor plug, it has the manifold one connected up, guessing it'* for the downstream one. Converter (and place for the sensor bung) were gone when I got it