Could someone please tell me where this hose goes to? The Blazer was given to me with the motor half way in, I have everything installed and good to go.... But this hose.. Thank you!

 

looks like vac hose . Possibly behind the motor by the distributor.

 

Someone modified it at one point in time. It's supposed to connect to a fitting on the intake manifold, near the PCV valve fitting in the driver side rocker arm cover. It supplies vacuum for 4WD and the HVAC systems.

 

As others have mentioned, that hose goes from the intake manifold on the drivers side down to a vacuum connection for the SMOG/secondary air pump. The hose that connects to the third part of the 'T' is a 7/16" vacuum hose and runs over to the area just behind the ABS controller/ABS pump. There it connects to another 'T' then to the A/C and the Vacuum Reservoir.

Just wanted to add that the connection for the vacuum reservoir is hard to find. It is in the fender and the connection is down under the ABS pump and has to be found by feel.